Washington: As more horrific pictures of abuse of Iraqi detainees were released, the embattled US begun a criminal probe into at least 37 deaths of prisoners in American custody in Iraq and Afghanistan, Pentagon officials said.

While some have been classified as deaths from natural or undetermined causes, eight have been classified as homicides. Several of those under investigation have been found to occur before or during probe sessions.

Of the total number of cases, 30 were inside US-run detention facilities and three were outside. Fifteen of the 30 cases were declared by US authorities to be deaths by natural cause or of undetermined cause, officials said.

Of the 15 other cases that happened inside detention facilities, four were categorised as justifiable homicides, two as homicides, and nine were still under active investigation, the officials said. Eight of those nine have been classified as homicides involving suspected assaults on detainees before or during questioning.

Six of the nine unresolved cases happened in Iraq including two at Abu Ghraib prison and three were in Afghanistan.

Meanwhile, the four-member Independent Panel to Review DoD Detention Operations met for the first time to begin its review and assessment work. Defence Secretary Donald Rumsfeld appointed the Panel on May 12 to review current and completed inquiries of detention operations.

The panel is scheduled to present its report to Rumsfeld and to the Senate and House Armed Services committees by the end of July.