China Labor Watch found human rights violations at an Apple supplier factory in China. China Labor Watch

Days before Apple is set to unveil its flagship iPhone 6, a labor rights group revealed "a number" of human rights violations at a supplier factory used to build iPhone and iPad parts.

China Labor Watch and Green America on Thursday said a factory owned by Catcher Technology Co. in Suqian, China, was found to have "serious health and safety, environmental, and human rights violations." The facility manufactures metal iPad covers and other parts for the fifth-generation iPhones, China Labor Watch said. It noted that during its investigation in August, 5oo to 600 workers from Catcher Suqian were transferred to the factory's sister location in Taizhou to work on the upcoming iPhone 6.

"The investigation of Catcher Technology raises serious concerns around working conditions in Apple's second-tier supplier factories," Todd Larsen, corporate responsibility director for Green America, said in a statement. "We knew that we needed to make this information public to encourage Apple to take immediate next steps in addressing toxins and unsafe working conditions in their factories as Apple continues to ramp up production of the iPhone 6."

See also

• Apple touts better working conditions as factory audits jump

• Apple halts use of two harmful chemicals in iPhone assembly

• Riots, suicides, and other issues in Foxconn's iPhone factories

• The environmental pitfalls at the end of an iPhone's life

• Digging for rare earths: The mines where iPhones are born

Apple, meanwhile, said it's "committed to ensuring safe and fair working conditions for everyone in our supply chain" and that it makes "it a priority to investigate every specific concern brought to our attention."

The condition of workers in the electronics industry has come under intense focus in recent months. Apple, Samsung, and many other large tech companies have faced fire over the treatment of the people building their phones, tablets, and other gadgets. As a result, the companies have pledged to do more to prevent the abuses. Apple even has said it plans to make more of its products in the US.

Thursday's report from China Labor Watch is far from the first time it has criticized Apple. The group has discovered many supplier issues in the past, and Apple has vowed to hold its partners to higher standards. It has done investigations of its own, published supplier reports, and instituted stringent policies on suppliers. In February, Apple's 2014 Supplier Responsibility report showed it had come a long way in improving working conditions across its international supply chain but that it still had more work to do.

The making of an iPhone (pictures)

Apple hires Foxconn to make most of its iPhones. Foxconn, in turn, hires hundreds of thousands of Chinese to do the labor. The jobs are in such high demand that workers line up at recruiters outside Foxconn's Zhengzhou factory. Many of the recruits in this group brought suitcases in case they land jobs at other Foxconn factories in China.

Foxconn's massive campus in Zhenghzhou, the capital of Henan Province, sprawls over 2.2 miles. The plants, where reportedly 130,000 people work, assemble an estimated 70 percent of all iPhones.

One Foxconn recruit at the Zhengzhou factory is Li Yue, a 21-year-old student at Henan Police College. She managed to land summer work, but in Taiyuan, a 10-hour bus ride away.

The amount of construction for Foxconn in Zhengzhou is staggering. Everywhere near the factory, new buildings are going up.

Another view of the construction activity. According to Chinese media reports, the company plans to grow from 130,000 workers now to 300,000.

In Zhengzhou, there are still some jujube trees, which produce the date-like fruit. But many have been replaced by Foxconn's sprawling factory complex.

Construction is moving so fast in Zhengzhou that street signs are going up without much copy editing. This sign shows directions to Foxconn, even if the English spelling isn't quite right.

Two of the roads on the Foxconn Zhengzhou campus take their names from two of the Chinese characters that make up the company's name -- Fu Street and Kang Road.

Many of the workers at Foxconn's Zhengzhou plant live in dormitories like these owned by the company. They generally live eight workers to a room, sleeping in bunk beds.

The streets near Foxconn's Zhengzhou dormitories are lined with vendors, selling food and clothes. Other than the vendors, most of the people walking these streets work at the Foxconn factory.

Foxconn assembly line workers wear these polo shirts at work. Streams of Foxconn-shirted workers flow in and out of factory gates at shift change time.

To accommodate the massive growth Foxconn plans for Zhengzhou, these buildings, most likely new dormitories, are going up near the current stock of dormitory buildings.

Foxconn operates factories in several Chinese cities, including two campuses in Shenzhen, the south China city that borders Hong Kong. This is the gate of the smaller of those two factories, in Shenzhen's Guanlan neighborhood, where the company employs 160,000 workers. Foxconn employs another 240,000 workers at the plant in the Longhua neighborhood.

After several suicides and suicide attempts at Foxconn's factories, including this one in Shenzhen's Guanlan neighborhood, the company installed netting to discourage employees from jumping off its buildings.

Foxconn is not the only contract manufacturer to assemble iPhones. Apple also contracts with Pegatron to build iPhones at this factory in Shanghai.

China Labor Watch, which was founded in 2000 and has since conducted a number of investigations in to Chinese factories, said that it investigated the same Suqian factory in April 2013 and found many of the same violations. At the time, the group reported its findings to Apple privately. Apple conducted its own investigation, the group said, and vowed to fix the problems, especially those related to worker safety.

"However, the results of CLW's subsequent undercover investigation of Catcher ... suggests that Apple and Catcher have done little to ensure that safety standards and other conditions have improved for Catcher's workers," China Labor Watch said. "In fact, the investigator going into the factory in 2014 discovered numerous additional violations that weren't found in 2013, as well as repeat violations from year to year, suggesting that conditions may actually be getting worse in the factory."

The issues found in Suqian in August included locked safety exits, a lack of safety training, hiring discrimination, excessive hours for workers, and forced overtime. China Labor Watch estimates each employee works six hours of unpaid overtime per month, resulting in roughly $290,000 in owed wages for all workers.

A factory worker in Apple's supply chain, from the company's Supplier Responsibility 2014 Progress Report. Apple

The group also found "significant" amounts of aluminum-magnesium alloy shreddings on the floor and dust particles in the air -- which pose a health and fire safety risk. And China Labor Watch said the factory dumps industrial fluids and waste into groundwater and nearby rivers. Employees also don't have proper equipment for handling toxic materials, the group said.

"CLW's investigation exposed more than 20 legal and ethical violations at the Catcher factory," Kevin Slaten, program coordinator at China Labor Watch, said in a statement. "This is exploitation by the factory and Apple for the sake of profit maximization."

Apple, meanwhile, acknowledged that Catcher's Suqian facility makes aluminum enclosures for MacBooks and iPads and said Apple's inspectors are there "constantly."

"We audit the facility's aluminum wet-polishing systems every month and consistently find that they exceed international safety standards," Apple said. "As a result of our quarterly fire-safety inspections, the most recent of which happened last week, Catcher has made same-day repairs of broken and expired fire extinguishers, unblocked corridors and fire exits, and added missing emergency exit signs."

Apple noted that its inspectors have found some areas for improvement and are working with Catcher "to develop a corrective action plan." They had scheduled a follow-up visit for next month but sent inspectors to the factory immediately after receiving China Labor Watch's report.

"Our suppliers must live up to the toughest standards in the industry if they want to keep doing business with Apple," the company said.

The trail of an iPhone's demise (pictures)

Apple's Asian revenue has soared in recent years, particularly since the iPhone's launch in China in 2009. This Apple store in Shanghai, along the well-traveled Nanjing Road, is frequently packed.

In Chinese cities that don't have Apple stores, consumers visit electronics marketplaces such as the SEG Electronics Market in Shenzhen. This is a vendor who sells both legitimate iPhones and fakes.

This "iPhone" is a fake, something the vendor cheerfully acknowledges. It's obvious because the writing on the back reads, "Designed by Apple in California. Assembled in U.S.A." Of course, no iPhones are assembled in the United States. The price: 650 renminbi or about $102.

This phone is an obvious Apple fake. It doesn't even try to resemble the iPhone, except for the spelling of the product's name. The letters may be different, but to non-English readers, they look awfully familiar. The vendor said this phone offers parents a way to appease children who want an iPhone without spending the money required. Its price: 400 renminbi or about $63.

When consumers buy a new mobile phone, they often unload their old one. In China, they can sell them to buyers like the man here, sitting behind the stand in front of the SEG Electronics Market in Shenzhen. He offered 2,300 renminbi, about $362, for an iPhone 4S.

Buyers of used mobile devices in China fix what they can to resell. The broken gadgets they can't fix are often taken to recycling operations, such as this one in Guangzhou, in south China. Many of those recyclers don't have modern equipment to properly handle the electronic waste.

Workers at this chop shop, an electronics recycling operation in Guangzhou, China, are tearing apart computers and computer monitors. Some said they also take apart broken mobile devices. They separate the plastic, the metals, and the wires. One environmental activist said the separated pieces are taken to other operations where they are melted so they can be resold, a "primitive" process that he said can release dangerous toxins.

At this recycling operation in Guangzhou, China, a worker, using a screwdriver, separates clear plastic pieces from black ones on a computer disk drive cover. The black plastic will likely be melted, though probably not in modern facilities, and resold.

On a day when both the humidity and temperatures were high, workers at this Guangzhou, China, electronics recycling operation had a fan to stay cool.

Workers at an electronics recycling operation in Guangzhou, China, separate plastic, metals, and wires as they pull apart computers. Their workplace includes makeshift stools made from old computer monitors.

Du Huanzheng, a professor at Jiaxing University near Shanghai, believes that electronics manufacturers should bear the cost of recycling products they sell in China.

Here's Apple's full statement:

Update, 8:48 a.m. PT: Adds Apple's comment.