The man, who was detained July 23 on his return from the base at Guantanamo and is being held at Vandenberg Air Force Base in California, was identified by the Pentagon as senior airman Ahmad I Al Halabi, a 24-year-old Muslim from Detroit.

NBC News reported that an indictment charges Al Halabi was sending intelligence, names and serial numbers by e-mail to a known enemy, and that a laptop he was carrying had 180 notes to be delivered to Syria.

The indictment claims he was carrying two handwritten notes from detainees with details of US intelligence gathering and plans for the US war on terrorism, NBC said.

Moreover, it said he was carrying details of military flights into and out of Guantanamo and maps of military installations there, the network reported.

The Air Force refused comment on the indictment, and said his arrest and a preliminary hearing was kept secret "to protect ongoing investigations."

Al Halabi was charged with 32 counts of espionage, aiding the enemy, failing to obey a lawful order, bank fraud, and making a false official statement, said Major Michael Shavers, a Pentagon spokesman.

The penalty for aiding the enemy is "death or such other punishment as a court-martial or military commission may direct," according to the Uniformed Code of Military Justice.

News of Al Halabi's arrest follows the disclosure over the weekend that an army chaplain at the Guantanamo detention center, Captain James Yee, was arrested September 10 on suspicion of espionage.

Asked whether the two were linked, Shavers said, "Only in the sense that they were there at approximately the same time."

Some 660 prisoners, most of them captured in Afghanistan in military operations against Taliban and al-Qaeda fighters, are being held at the maximum security facility.

Like Yee, Al Halabi was arrested at Jacksonville Naval Air Station on his arrival on a military flight from Guantanamo Bay, Shavers said.

Al Halabi was taken to Travis Air Force Base in California, where he was assigned to the 60th Logistical Readiness Squadron, and then transferred to Vandenberg Air Force Base where a preliminary hearing was held September 15-18 into the charges against him, the air force said.

The Article 32 hearing, which is similar to a civilian grand jury process, is held to determine whether there is sufficient evidence to warrant court martial or some other legal proceeding.

The air force said an investigating officer was preparing a report on his investigation, which will be made to Brigadier General Bradley Baker, commander of the 60th Air Mobility Wing, who will decide whether to convene a court martial.

Yee, a 35-year-old Chinese-American and Muslim convert, also was reported to have been found with classified documents, including a detailed sketch of the Guantanamo detention facility.

Yee was assigned to the Guantanamo Bay camp last November to serve as religious counselor to the inmates there, and as an adviser on Muslim affairs to base commanders.

A West Point graduate, he resigned from the army before going to Syria to receive religious training. He rejoined the army on his return.

The arrests indicate the United States fears moles within the armed forces have penetrated one its prime prisons for suspected Taliban and al-Qaeda fighters.

The Guantanamo naval base was chosen as the site of the prison precisely because it was both inaccessible to the outside world and beyond the jurisdiction of US courts.

Even the names of the prisoners, as well as their exact numbers, have been kept secret as US interrogators pump them for intelligence.

The positions of chaplain and translator would offer sensitive access to prisoners and possibly intelligence gathered in interrogations.

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