Members of a Facebook group for US border agents reportedly mocked the death of a migrant child in custody and posted racist comments about congresswomen inspecting the facilities.
In one post, the group of current and former border patrol agents referenced a news story about a 16-year-old Guatemalan who died in Border Patrol custody, with comments underneath such as "Oh well" and "If he dies, he dies."
Another post contained a mock-up of the Democratic congresswoman engaging in oral sex with a detained migrant.
The existence of the Facebook group, named "I'm 10-15", was revealed by the non-profit news site ProPublica. 10-15 is Border Patrol code for "aliens in custody."
The US Customs and Border Protection (CBP) agency said on Monday that it has launched an investigation into the group, appearing to confirm that some of its employees were involved.
In a statement the CBP said it had been "made aware of disturbing social media activity hosted on a private Facebook group that may include a number of CBP employees."
Members of the group also posted derogatory comments about female Hispanic lawmakers, including fake sexually explicit photo montages of Ms Ocasio-Cortez, who has been outspoken on the treatment of migrants in US facilities.
The members discussed throwing burritos at the Hispanic members of Congress who were visiting a detention facility in Texas on Monday.
Border Patrol chief Carla Provost denounced the "inappropriate" posts in the Facebook group and the CBP, which oversees the Border Patrol, said it had launched an investigation.
"These posts are completely inappropriate and contrary to the honour and integrity I see - and expect - from our agents day in and day out," Ms Provost said. "Any employees found to have violated our standards of conduct will be held accountable."
Asked about the @CBP agents @Facebook group with derogatory and vulgar comments, @POTUS (who may not be familiar with what the questioner was referring to) replied: The Border Patrol -- they're patriots. They're great people. They love our country. They know what's coming in."— Steve Herman (@W7VOA) July 1, 2019
The group was created in August 2016 and has some 9,500 members. ProPublica said it was able to link the participants in the controversial posts to seemingly legitimate Facebook profiles belonging to Border Patrol agents, including a supervisor based in El Paso, Texas, and an agent in Eagle Pass, Texas. The website said it has provided the names of three agents who appear to have participated in the online discussions to the CBP.
Ms Ocasio-Cortez, who has been a frequent critic of the CBP, said the revelations would not impact her planned visit to facilities housing migrants along the US-Mexico border on Monday.
"There are 20,000 TOTAL Customs & Border Patrol agents in the US," Ms Ocasio-Cortez said in a tweet.
"9,500 CBP officers sharing memes about dead migrants and discussing violence and sexual misconduct towards members of Congress," she said. "How on earth can CBP's culture be trusted to care for refugees humanely?"
Now I’ve seen the inside of these facilities.— Alexandria Ocasio-Cortez (@AOC) July 1, 2019
It’s not just the kids. It’s everyone. People drinking out of toilets, officers laughing in front of members Congress.
I brought it up to their superiors. They said “officers are under stress & act out sometimes.” No accountability.
The New York representative also decried the conditions she found at the migrant facilities she visited.
"It's not just the kids. It's everyone. People drinking out of toilets, officers laughing in front of members of Congress," the congresswoman said.
"This has been horrifying so far," she said. "It is hard to understate the enormity of the problem."
"We're talking systemic cruelty w/a dehumanizing culture that treats them like animals," she said.
Border Patrol officials have said they are overwhelmed by the numbers of refugees crossing the southern US border.
Arrivals of undocumented migrants have surged in recent months, with 144,000 taken into custody in May alone.