The House Oversight Committee is seeking documents from U.S. Customs and Border Protection as it investigates secret Facebook groups in which dozens of current and former employees allegedly shared racist and sexist memes and joked about migrant deaths.

The move suggests that the panel’s chairman, Rep. Elijah E. Cummings, is not backing down from his investigations into the Trump administration, despite the president’s recent attacks on the Maryland Democrat and his district.

In a letter Wednesday to acting customs and border protection commissioner Mark Morgan, Cummings voiced alarm that some of the agents involved in the Facebook groups may still be on the job.

“The Committee is concerned that Border Patrol agents and other CBP employees who wrote posts disparaging immigrants may still be working with immigrants and children,” Cummings wrote in the letter.

Cummings said members of the Facebook groups had made “racist, sexist and xenophobic comments relating to immigrants and Members of Congress” and requested that CBP provide all documents related to the matter by Aug. 14, including the postings themselves, the names and titles of every CBP employee investigated, and records of any employment action taken against them.

Cummings also reiterated his request for a briefing on the matter, setting a deadline of Aug. 7.

Earlier this month, CBP announced that it is investigating 62 current employees and eight former employees for possible misconduct over their alleged participation in the Facebook groups. The groups include “Real CBP Nation” and “I’m 10-15,” which is Border Patrol code for “aliens in custody.”

The announcement came after ProPublica published a report about content posted to one of the private online forums. According to Politico, CBP officials were already aware of the groups before they were reported by news outlets, prompting outrage from lawmakers and advocates for immigrant rights.

Some of the most recent offensive Facebook postings concerned a visit by members of Congress to a Border Patrol station in Clint, Tex. One post carried an illustration of Rep. Alexandria Ocasio-Cortez (D-N.Y.) performing a sex act at a Border Patrol facility; another portrayed a smiling President Trump pushing the congresswoman’s face toward his lap.

In testimony before Cummings’s committee this month, acting homeland security secretary Kevin McAleenan called the postings “unacceptable” and said CBP is “moving very quickly to hold people accountable for conduct that doesn’t meet our standards.” He added that some of the agents who participated in the groups had been placed on administrative duties, although he did not provide details.

Abigail Hauslohner contributed to this report.