The Pentagon's Southern Command will head up the investigation into allegations of prisoner abuse at Guantanamo Bay brought by a Marine Sergeant who first told her story publicly Thursday on ABC News.

Southcom, which oversees military activities in the Caribbean and Latin America, issued a statement to ABC News saying it "will fully cooperate with the Inspector General to learn the facts of the matter and will take action where misconduct is discovered."

The complaint was filed by Marine Lt. Col. Colby Vokey, defense counsel for one of the detainees.  It is based on a sworn affidavit by Sgt. Heather Cerveny (pictured above), his paralegal, who states that during a visit to the base in late September, she heard a number of U.S. Navy guards speak openly of abusing prisoners.

In an exclusive interview with ABC News, Sgt. Cerveny said one guard talked about punching a detainee in the face, and another said he smashed a prisoner's head into the cell door.

"Everyone in the group laughed at all their stories of beating detainees," she recalled.  "None of them looked like they cared. None of them looked shocked by it." 

A spokesman for the Pentagon Inspector General's office said Friday, the complaint was filed on Oct. 6, and "as soon as we got this, it was turned around and tasked to Southcom."