The US Justice Department said on Friday that it would drop its efforts to keep imprisoned one of the youngest Guantanamo Bay captives, but said he now would face a criminal investigation.

The decision came in the case of Afghan prisoner Mohammed Jawad, who had asked a federal judge in Washington to order his release from the US military prison in Cuba.

The Afghan Independent Human Rights Commission has said Jawad was only about 12 when arrested in 2002, but the Pentagon disputes that and has said bone scans indicated he had turned 18 when sent to Guantanamo in early 2003.

Jawad had been charged in a military court with throwing a grenade that injured two US soldiers and their Afghan interpreter at a bazaar in Kabul in December 2002.

US District Judge Ellen Segal Huvelle, who has been hearing Jawad's case seeking his release, ruled on July 17 that all his statements, including his confession, after his arrest must be thrown out because they had been obtained through torture.

She gave the Justice Department a July 24 deadline to describe the legal and factual basis for its case that Jawad should remain imprisoned.

The Justice Department said on Friday that the government will no longer treat Jawad as "detainable" under a law adopted after the September 11 attacks.

As a result, the Defense Department is "taking steps to house" Jawad at an appropriate camp facility at Guantanamo, it said.

But Attorney General Eric Holder has directed that a criminal investigation of Jawad continue and be conducted quickly into the allegations he threw a grenade at US military personnel, the Justice Department said.

It said the investigation is based on multiple eyewitness accounts, including videotaped interviews, that were not previously available for the record in the case.

Jawad is among the approximately 200 Guantanamo prisoners who have challenged their detention in federal court. Of the cases decided so far, 26 prisoners have been ordered released while judges upheld the continued detention of five detainees.

President Barack Obama has ordered the closing of the internationally condemned Guantanamo prison by January. It now holds 229 detainees.

The prison was set up in 2002 to hold foreign prisoners in the US war on terrorism that then-President George W. Bush declared after the hijacked plane attacks on the United States on September 11, 2001.

Jawad faced attempted murder charges in the now-stalled Guantanamo war crimes tribunals. Obama seeks to revive the military trials after changes in the rules to make them fairer.

A military judge previously threw out most of the evidence against Jawad. The judge ruled Jawad's confession to Afghan authorities was obtained through death threats that constituted torture and his subsequent confession to U.S. interrogators was the fruit of that torture and could not be used as evidence.

The military prosecutor assigned to the case quit, alleging the US government was suppressing evidence that cast doubt on Jawad's guilt.

Jawad's case also showed that a sleep-deprivation technique continued at Guantanamo months after the prison camp commander had ordered it halted.

Other evidence in the case indicated Jawad was beaten and chained to the wall while in US custody in Afghanistan then subjected to extreme isolation at Guantanamo, where he tried to hang himself in his cell.