The US military is checking complaints by an Afghan police officer that he was stripped naked, beaten and photographed at a US base in Afghanistan.
Rights groups claim US detentions violate international law
The alleged incidents occurred at a US base in Gardez, east of the capital Kabul, in August 2003.
The New York Times quoted the officer as saying he was subjected to sexual abuse, taunting and sleep deprivation.
The investigation follows revelations about American soldiers' treatment of prisoners in Iraq.
Former police colonel, Sayed Nabi Siddiqui, 47, told the New York Times he was wrongly detained on 15 July after reporting police
He said he was detained in three prisons over 40 days after someone accused him of being a member of the Taleban.
Mr Siddiqui said he was abused at all the bases, but the worst case was at Gardez.
'Challenges and problems'
In a press statement, US Ambassador Zalmay Khalilzad said he was not aware of the existence of any photos of the alleged Gardez incident.
"To the best of our knowledge this is the first time anyone in the military chain of command or the United States Embassy has heard of this alleged mistreatment," he said.
Barno rejected appeals for greater access to Afghan prisoners
On Tuesday, the top US military commander in Afghanistan, Lt Gen David Barno, rejected an Afghan human rights group's demand to carry out checks on detainees in US custody in the country.
General Barno said the army had investigated "challenges and problems" at some bases and had decided to switch prisoners to the main US facility at Bagram, north of Kabul.
At least 300 people, the majority of them Afghans, are believed to be held at Bagram and an unknown number at other sites.
In March, a Human Rights Watch report said the US detention system in Afghanistan violated international law.
Prisoners are being switched to the Bagram air base
Two Afghans died at Bagram in December 2002, with autopsies suggesting injuries from blunt implements.
The US military said it had had difficulty gathering evidence and has yet to publish a report.
Another Afghan died in June last year at a detention centre in Kunar province, in the east.
Concerns about US treatment of detainees in Afghanistan are not new but the images of prisoner treatment in Iraq have highlighted them again.
Some newspapers have demanded investigations into whether US forces have been behaving in a similar way in Afghanistan.
The US only allows the International Committee of the Red Cross access to bases such as Bagram and the Red Cross reports are confidential.
Ahmad Zia Langari, of the Afghan Independent Human Rights Commission, says this lack of access leads people to think Iraq-style abuses are happening in Afghanistan.