A prisoner of Saudi Arabia at the Guantanamo Bay detention center who was questioned about attempting to enter the 9/11 hijackers has been shipped back to his home country for therapy for mental illness, said the Defense of Department.

Mohammad Ahmad al-Qahtani was passed back to Saudi Arabia in order to get treatment from the US-based in Cuba after a review board in which military and intelligence included and concluded he could be safely released after being in custody for 20 years.

As per his lawyer’s statement, the 46 years old prisoner had suffered from mental sickness, including schizophrenia, since childhood. The US dropped goals to try him after a Bush government legal official concluded he had been in torture at Guantanamo.

After his release, there are now 38 prisoners are left at the detention centre. He is the second person who is coming out from detention in the presence of Joe Biden, who has said he intends to close the facility.

At the same time, the United States appreciated the willingness of Saudi Arabia and others to support ongoing US efforts toward a conscious and complete process concentrated on responsibly decreasing the detainee population and eventually closing of the Guantanamo Bay facility,” the Department of Defense said in a statement Monday while announcing the releasement of al-Qahtani.

In contrast, about 50 per cent of men were held there and were cleared for their release, and no other decision has been made about what to do with the people who left, including those who still face trial by military commission.

The Defense Ministry stated that the Congress intended to transmit al-Qahtani in February, provoking outrage from some Republicans.

In August 2001, al-Qahtani was turned away from the United States at the Orlando airport by immigration officers suspect of his travel.

According to previously released documents, the lead September 11 hijacker, Mohammed Atta, was going to take him up to take part in the plot.

However, US forces captured him when he was in Afghanistan and sent him to Guantanamo, where he was targeted to brutal interrogations that the Pentagon legal official in charge of war crimes commissions said amounted to torture.