U.S. Southern Command spokesman Bob Appin says the 37-year-old prisoner was not breathing when guards found him Wednesday. Appin says the guards tried without success to resuscitate him.
The prisoner went by only one name: Inayatullah. He had been held at the U.S. base in Cuba since September 2007.
He is the eighth prisoner to die at the detention center since January 2002, when the U.S. began using the U.S. Navy base in southeastern Cuba to hold captured detainees suspected of links to al-Qaida or the Taliban. Five other deaths were declared suicides. Two others were from apparently natural causes.