MIAMI - A prisoner was found dead of undetermined causes at the Guantanamo Bay US naval base, the US military said on Monday.

The unidentified prisoner, whose name and nationality were not disclosed pending notification of family, died on Saturday, according to the US Southern Command, which oversees the base in eastern Cuba. He was the ninth captive to die at the detention camp since it opened in 2002.

"While conducting routine checks, Joint Task Force-Guantanamo guards found the detainee unconscious and unresponsive. The guards immediately performed first aid and summoned medical personnel to the scene," the Southern Command said in a news release.

Medical corpsmen tried to revive him and took him to the base hospital, where he was pronounced dead, the news release said. His remains will be brought home once an autopsy is complete, it said.

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