US officials are investigating a secret Facebook group where border patrol members allegedly posted racist and sexist jokes about migrants and others.
The private group had about 9,500 members, including former and current border patrol agents, ProPublica reported.
Some posts mocked migrant deaths, while others targeted Latino members of Congress, ProPublica said.
The Border Patrol chief has called the posts "completely inappropriate".
"Any employees found to have violated our standards of conduct will be held accountable," Carla Provost said.
The group was called "I'm 10-15", ProPublica said - 10-15 being Border Patrol code for "aliens in custody".
'Throw burritos at them'
According to ProPublica, members of the group mocked Latino members of Congress who visited migrant detention centres in Texas on Monday.
Democrats Alexandria Ocasio-Cortez and Veronica Escobar were among those said to have been called "hoes" and "scum buckets" in the private postings.
In one post, a member reportedly suggested throwing burritos at them, while another shared a doctored image depicting Ms Ocasio-Cortez performing a sex act on President Donald Trump.
The BBC was not able to independently verify the existence of the private group, which is not publicly accessible on Facebook.
Matthew Klein, an assistant commissioner at the CBP, said the Department of Homeland Security had launched a code-of-conduct investigation into the group.
He said a number of CBP agents may be members of the group.
Ms Ocasio-Cortez said the posts did not surprise her, and that they were "indicative" of what she had seen while visiting the migrant detention centre on Monday.
"I see why CBP officers were being so physically and sexually threatening towards me," she tweeted after the trip.
'Forced to drink from toilets'
On Twitter, Ms Ocasio-Cortez said that border patrol officers had told women in cells to "drink out of the toilets".
She added that during the visit, she "forced" herself into a cramped cell where the women inside "described their treatment at the hands of officers as 'psychological warfare'".
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.
After critics shared a photo of similar toilets in another such facility - with a sink attachment on top labelled "potable water" - Ms Ocasio-Cortez said the one she saw was "not functioning" at the time.
"So the women were told they could drink out of the bowl," she tweeted.
As @AOC noted, people held in CBP custody are often asked to drink out of toilets, which is disgusting for those held in those facilities. Here's an example of one cell where a toilet/fountain in a cell has "Agua Potable" written above it. pic.twitter.com/dUJKzWaOHH— Aaron Reichlin-Melnick (@ReichlinMelnick) July 1, 2019
A Trump administration official, who did not wish to be named, told CBS News that "the toilets are connected to the sinks and the sinks dispense safe drinking water.
"The sink on top of the toilets broke. But as soon as the sinks broke, border patrol put out jugs of water for migrants to drink right when that happened. The jugs were right there for everyone to drink."
Ms Ocasio-Cortez and other lawmakers toured detention centres days after a harrowing picture of a drowned man and his daughter on the US-Mexico border brought the migration crisis into sharp focus.
Last month, the New York congresswoman stoked controversy after comparing migrant detention centres to "concentration camps".
What's the reaction?
Chairman of the Congressional Hispanic Caucus Joaquin Castro condemned the secret Facebook page as "vulgar, disgusting and vile".
"That shows, unfortunately, that there are many within CBP who've become desensitised to the point of being dangerous to the migrants in their care."
This moment captures what it’s like for women in CBP custody to share a cramped cell—some held for 50 days—for them to be denied showers for up to 15 days and life-saving medication. For some, it also means being separated from their children. This is El Paso Border Station #1. pic.twitter.com/OmCAlGxDt8— Joaquin Castro (@JoaquinCastrotx) July 1, 2019
Senator Cory Booker, a Democratic presidential candidate, said on Tuesday that he was introducing a plan to "virtually eliminate migrant detention".
He called the facilities "for-profit prison that should not exist", and said that as president, he would improve the facilities and close any that do not meet his standard.
Since taking office in 2017, President Trump had adopted tougher policies in an attempt to reduce the number of undocumented migrants.
But officials say his administration's crackdown, and the recent increase in Central American migrant arrivals, has led to a strain on enforcement resources.
Apprehensions on the border reached 132,000 in May 2019, the highest levels in over a decade, according to US government figures.
Earlier this month, Mexico reached a deal with the Trump administration to try to stem the flow of undocumented migrants travelling to the US.
Last month a US Justice Department lawyer disputed in court whether detained migrant children are entitled to toothbrushes and soap.
In February, Mr Trump declared an emergency on the country's southern border, saying it was necessary to tackle what he said was a crisis there.
Last week, the US Congress approved a $4.5bn (£3.5bn) humanitarian aid package for the US-Mexico border.