Attorney General Merrick Garland, flanked by a pair of New York prosecutors, announced charges Friday against four Chinese companies and eight employees accused of selling chemicals to fuel the deadly U.S. fentanyl market.

More than 200 kilograms of “pre-cursor” chemicals used to create the deadly drug were seized, an amount that could create enough doses to kill 25 million Americans, said Garland at a Washington news conference.

The overseas businesses “are supplying the cartels with the building blocks they need to manufacture deadly fentanyl,” he said. “Our agents and prosecutors are working relentlessly.”

The infamous Sinaloa Cartel and the Jalisco New Generation Cartel, both based in Mexico, are among the drug operations increasingly turning to the products peddled by the Chinese operations, officials said.

Three indictments in the probe were returned in the Manhattan and Brooklyn federal courts — the first U.S. prosecutions charging the China-based chemical manufacturing businesses.

Fentanyl deaths have been ravaging New York. Overdose deaths climbed citywide — from just under 1,500 overdose deaths in 2019 to around 2,670 two years later in 2021, according to a recent city report. The COVID pandemic aggravated a problem already on the rise: In 2015, just 942, or 13.8 of every 100,000 city residents, died of an overdose. The report found fentanyl was present in 80 percent of all overdose deaths.

Garland and other officials described the arrests as attacking the fentanyl supply chain at its source.

The brazen Amarvel Biotech operation openly advertised via social media, going as far as guaranteeing 100% stealth shipping in some cases, said Garland.

The pre-cursors were often sent with masking molecules to make the lethal packages appear benign.

During the eight-month undercover Drug Enforcement Administration investigation, authorities seized more than 200 kilograms of the chemicals — much of it sent to New York, officials said.

The Wuhan-based Amarvel additionally used deceptive packaging, shipping product marked as dog food, cosmetics and motor oil, to avoid detection, authorities alleged.

Two additional indictments in Brooklyn targeted another three companies on similar offenses, officials said.

“We’ve charged a Chinese pre-cursor chemical company,” said Manhattan Federal Prosecutor Damian Williams. “And that’s not all. We’ve charged and arrested some of the individuals who work at the company.

“They’re in American handcuffs. And they’re going to face justice in an American courtroom.”

The ongoing U.S. overdose epidemic claimed more than 100,000 Americans in 2022, with fentanyl now the leading cause of death among U.S. residents between the ages of 18 to 49.

“This prosecution shows that the companies and individuals who fuel our nation’s deadly opioid epidemic, wherever they are located, will be found and prosecuted to the full extent of the law,” said Brooklyn Federal Prosecutor Breon Peace.

Two of the Amarvel defendants were arrested on June 8 after they were expelled from Fiji and arraigned a day later in Hawaii, with both expected to appear in Manhattan Federal Court.

The company’s last shipment arrived at a warehouse in Los Angeles just last month.

“These companies and individuals are alleged to have knowingly supplied drug traffickers, in the United States and Mexico, with the ingredients and scientific know-how needed to make fentanyl,” said Ann Milgram, head of the Drug Enforcement Administration.