Around 660 al-Qaeda and Taleban suspects are held in Guantanamo Bay

He has not been charged, but it is believed that he is suspected of espionage.

Captain James Yee has been held since 10 September as part of a military investigation, said a spokesman for Southern Command, which oversees the US base in Guantanamo Bay, Cuba.

A senior law enforcement official told the Associated Press news agency that agents from the Federal Bureau of Investigation confiscated classified documents Mr Yee was carrying and questioned him before he was handed over to the military.

The chaplain was arrested as he stepped off a plane at Jacksonville Naval Air Station in the US state of Florida. Officials say the investigation is ongoing.

Mr Yee, a Chinese-American who graduated from West Point military academy, was assigned to the naval base at Guantanamo Bay in November, Southern Command spokesman Captain Thomas Crosson said.

Around 660 al-Qaeda suspects and alleged members of Afghanistan's former Taleban regime are currently being detained at the Camp Delta military prison in Guantanamo Bay.