The Pentagon has determined four more prisoners at Guantanamo Bay (search), Cuba, no longer pose much of a threat and plans to release them, a senior official said Friday.

No information on those four was available. The State Department is making arrangements to send them to their home countries, said Rear Adm. James M. McGarrah, who oversees the reviews of prisoners and whether they should remain at Guantanamo, told reporters at the Pentagon.

Their fate was determined by a quasi-judicial process called an administrative review board, which the Pentagon created after human rights groups complained about the indefinite nature of the detentions at the U.S. naval base.

A three-officer board decides whether the prisoners remain enough of a threat to justify keeping them at Guantanamo. Their home governments and families are allowed some input, but they are not afforded legal representation. Each prisoner can be released, transferred to his home government or kept in detention.

Gordon England (search), the acting deputy defense secretary, has approved 70 decisions of the board: the four releases, 25 transfers and 41 continued detentions, McGarrah said. The board intends to review the cases of most of the rest of the prisoners at Guantanamo at least once a year.

About 520 prisoners remain at Guantanamo; another 234 have been released or transferred to the custody of their home governments through various processes. Of those, 12 have returned to terrorism, McGarrah said.

In all, sixty prisoners who remain at Guantanamo are slated for release or transfer, according to Navy spokeswoman Capt. Beci Brenton. Some of their fates were decided before the administrative review process began.

In some cases, the U.S. government does not received satisfactory assurances they won't be mistreated once they arrive in their home country, leaving them in a legal limbo at Guantanamo. McGarrah said these people have more privileges than the rest of the prison population.

The people held at Guantanamo are mostly Afghans, Pakistanis and others captured after the U.S. invasion of Afghanistan in October 2001. They were labeled "enemy combatants (search)," which the Bush administration decided did not afford them status as prisoners of war under the Geneva Conventions (search). Only a few have been charged with any crime.