In a Twitter message Thursday, Rep. Alexandria Ocasio-Cortez branded the leadership of U.S. Customs and Border Protection as liars after a news site reported that CBP officials knew much longer than they claimed about a Facebook group on which some past and current CBP employees had posted offensive material.

According to Politico, top CBP officials had known about the offensive posts “for up to three years” – even though officials claimed this week that they had only recently learned about them.

“Looks like CBP lied,” Ocasio-Cortez charged Thursday, one day after the Politico story appeared. “Reporting shows they knew about it for *years.* This is a big deal.”

It was the latest criticism by Ocasio-Cortez, who previously asserted that border-protection personnel have been forcing detained migrants to drink toilet water inside U.S. detention facilities – a claim that some current and former immigration officials have disputed.

Meanwhile, Republicans, including President Trump, have countered that Democrats like Ocasio-Cortez have been complaining about border conditions caused in part by their own opposition to a $4.6 billion bill that ultimately was approved by Congress and signed by Trump on Monday, according to the Washington Times.

Wednesday’s Politico story followed a report Monday by ProPublica that described the so-called “I’m 10-15” site, which reportedly has 9,500 members. (“10-15” is a Border Patrol designation for “aliens in custody,” according to the report.)

According to ProPublica, the site includes jokes about the deaths of migrants and Latino members of Congress, and includes vulgar illustrations of Ocasio-Cortez and other public figures.

After the ProPublica story appeared Monday, CBP officials condemned the Facebook posts.

“These posts are completely inappropriate and contrary to the honor and integrity I see — and expect — from our agents day in and day out," U.S. Border Patrol Chief Carla Provost said in a statement to Fox News. "Any employees found to have violated our standards of conduct will be held accountable.”

"Any employees found to have violated our standards of conduct will be held accountable.” — U.S. Border Patrol Chief Carla Provost

Recently appointed acting Homeland Security Secretary Kevin McAleenan also denounced the posts in a Twitter message.

“Reporting this week highlighted disturbing & inexcusable social media activity that allegedly includes active Border Patrol personnel. These statements are completely unacceptable, especially if made by those sworn to uphold the @DHSgov mission, our values & standards of conduct,” McAleenan wrote Wednesday.

Matthew Klein, assistant commissioner of the CBP’s Office of Professional Responsibility, said the Department of Homeland Security’s inspector general opened an investigation on Monday.

"Today, U.S. Customs and Border Protection was made aware of disturbing social media activity hosted on a private Facebook group that may include a number of CBP employees," Klein said. "CBP immediately informed DHS Office of the Inspector General and initiated an investigation."

But the Politico story on Wednesday cited prior instances of vulgar posts. It said that former Border Patrol chief Mark Morgan was alerted in 2016 to a post in which a CBP agent was shown to be simulating sex with a training mannequin, while other posts showed an agent holding what appeared to be a human skull and another agent seeming to be defecating in the desert.

Politico reported that a CBP spokesperson claimed that the posts were reported at the time to the agency’s Office of Professional Responsibility, which conducted an investigation but did not disclose the findings. The Facebook group, however, continued with newer posts added.

Morgan later became acting director of Immigration and Customs Enforcement (ICE). In June, he blasted Ocasio-Cortez, calling “reckless” her comparison of U.S. border facilities to “concentration camps.” On June 27, Morgan was named to become acting commissioner of the CBP, replacing John Sanders.

Speaking to Fox News, a CBP official maintained, in response to the Politico report, that the agency only learned of these posts following the ProPublica inquiry earlier this week – and not earlier.

One source described as a former official at the Department of Homeland Security also told Politico that neither DHS nor CBP should be expected to monitor all the social media posts of their employees.

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“Nobody in government can watch everything that’s being said about an entity in social media,” the DHS source said, according to Politico. “What gets posted at 5 p.m. today will be buried under thousands of messages tomorrow.”

“Nobody in government can watch everything that’s being said about an entity in social media. What gets posted at 5 p.m. today will be buried under thousands of messages tomorrow.” — DHS source, according to Politico

Earlier in the week, Ocasio-Cortez asserted that the number of CBP employees reportedly involved in the Facebook group shows the agency has “a violent culture,” not just “a few bad eggs.”

On Wednesday, Senate Minority Leader Chuck Schumer, D-N.Y., called for the Trump administration to remove top CBP officials over reports about the Facebook group.

Fox News’ Alex Pappas contributed to this story.