SAN JUAN, Puerto Rico - A Yemeni detainee at Guantanamo Bay has died of an "apparent suicide," U.S. military officials said yesterday.

The Joint Task Force that runs the U.S. prison in Cuba said guards found Muhammad Ahmad Abdallah Salih, also known as Mohammad Ahmed Abdullah Saleh Al-Hanashi, unresponsive and not breathing in his cell Monday night.

His is the fifth apparent suicide at the Guantanamo prison, which President Obama plans to close by January.

In a statement, the U.S. military said the detainee was pronounced dead after "extensive lifesaving measures had been exhausted."

The Yemeni prisoner had been held without charge at Guantanamo since February 2002. Military records show the alleged Taliban fighter was about 31.

The military said the remains would be autopsied by a pathologist from the Armed Forces Institute of Pathology. The Naval Criminal Investigative Service has launched an investigation of the incident.

The prisoner appeared to have joined the long-running hunger strike at Guantanamo, according to medical records previously released by the military. He weighed 124 pounds when first taken to Guantanamo, and was down to about 86 pounds in December 2005.

A prison spokesman, Navy Lt. Cmdr. Brook DeWalt, declined to discuss further details on the suicide or whether procedures had changed at Guantanamo as a result.