Washington (CNN) Acting Homeland Security Secretary Kevin McAleenan told lawmakers that there is an "aggressive" ongoing investigation into the secret Facebook group of current and former Border Patrol agents that sparked outrage earlier this month, responding to a question from Rep. Alexandria Ocasio-Cortez during a contentious House Oversight Committee hearing Thursday.

The group, which was originally uncovered by ProPublica , featured jokes about migrant deaths and derogatory posts and images of Latina members of Congress.

"Those posts are unacceptable," McAleenan said. "They are being investigated but I don't think that it's fair to apply them to the entire organization or that even the members of that group believed or supported those posts."

Ocasio-Cortez -- who was personally attacked in a sexually graphic post in the group -- asked McAleenan about what he knew about the group prior to the media reports and whether any agents involved were still on the force.

McAleenan said that he directed an investigation "within minutes" of learning about the group from reports and that the department has placed several agents on administrative leave and issued dozens of cease and desist orders.

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