(CNN) -- A detainee at the U.S. military prison at Guantanamo Bay, Cuba, died over the weekend, U.S. Southern Command announced Monday.
The detainee was found unresponsive Saturday afternoon during a routine check, Southern Command said in a news release.
Medical personnel were summoned and provided emergency treatment before taking the detainee to Naval Hospital Guantanamo.
"After extensive lifesaving measures had been performed, the detainee was pronounced dead by a physician," the Southern Command statement said.
The cause of death is under investigation. Suicide has not been ruled out, according to Southern Command Sgt. Shanda De Ande.
The identity of the detainee is being withheld pending notification of the prisoner's family and government.
CNN's Dave Alsup contributed to this report.