SAN JUAN, Puerto Rico - A U.S. Army colonel investigating allegations of prisoner abuse at Guantanamo Bay has returned to his base in Miami to prepare a report after spending nearly a month at the detention center in Cuba, a military spokesman said Wednesday.

Col. Richard Basset, who arrived at Guantanamo on Oct. 18, was appointed after a Marine sergeant filed a sworn statement that guards she met at a Guantanamo bar spoke of hitting detainees and denying them water.

Basset is expected to file a report on his findings in the coming days to the commander of the U.S. Southern Command in Miami, which oversees the naval base where about 430 detainees are held on suspicion of links to al-Qaida or the Taliban.

"He's in the final stages of the investigation," command spokesman Jose Ruiz said by telephone from Miami.

Ruiz said he could not provide details of how Basset spent his time at Guantanamo. Basset had been given authority to interview any member of the military Joint Task Force, which runs the prison.

The Pentagon's Inspector General's office ordered the investigation after Marine Lt. Col. Colby Vokey, who represents a Guantanamo detainee, filed a complaint alleging detainee abuse was ongoing at the prison.

Vokey attached the statement from his paralegal, Sgt. Heather Cerveny, in which she said the guards she met bragged about beating detainees and described it as common practice.