San Juan, Puerto Rico ? The U.S. Southern Command on Friday launched an investigation into “credible allegations” that guards at Guantanamo Bay abused detainees, and appointed an Army colonel to lead the probe.

The Pentagon’s Inspector General’s office said Friday that it had ordered the Miami-based Southern Command to investigate after Marine Lt. Col. Colby Vokey, who represents a detainee at the U.S. naval base in eastern Cuba, filed the “hot line” complaint last week.

Vokey attached a sworn statement from his paralegal, Sgt. Heather Cerveny, 23, in which she said several guards in a bar at Guantanamo Bay bragged about beating detainees and described it as common practice.

“Other ones of them were talking about how when they get annoyed with the detainees, about how they hit them, or they punched them in the face,” Cerveny said Thursday night. “It was a general consensus that I (detected) that as a group this is something they did. That this was OK at Guantanamo, that this is how the detainees get treated.”

Cerveny visited the U.S. Naval Base in Cuba last month and said she spent an hour with the guards at the club. The guards quit discussing beating detainees after finding out she works for a detainee’s legal team.

In her complaint, she wrote: “From the whole conversation, I understood that striking detainees was a common practice.”

The military Joint Task Force that runs the camps in Guantanamo Bay pledged to work with investigators from the Southern Command, which oversees U.S. military operations in the Caribbean and Latin America.