KABUL (Reuters) - A detainee being held by troops from the NATO-led force in Afghanistan was found dead in his holding cell, and an investigation is underway, the force said in a statement Monday.

The man was captured during a military operation by the International Security Assistance Force (ISAF) Saturday and was “found dead” the following day in his cell in Kandahar province, ISAF said in a statement.

It did not give any further details.

Prisoner abuse and deaths of detainees while in the custody of foreign troops is a sensitive subject for many Afghans after U.S. troops beat to death two prisoners in 2002 at the old Bagram prison at the U.S. Bagram Air Base north of Kabul.

That jail, which was set up to hold prisoners from the campaign against the Taliban after the September 11 attacks, was replaced earlier this year by a $60 million prison -- also on Bagram Air Base -- which Washington says meets international standards.

Saturday, a report by U.S.-based think-tank Open Society Foundations said former detainees held at a secret U.S. prison at Bagram, separate to the main jail, had reported abuse at the hands of the U.S. military.

In the report, former detainees said jailers mistreated them by depriving them of natural light, failing to provide proper food and withholding Red Cross visits.

A spokeswoman for U.S. military detention operations said the International Committee of the Red Cross was aware of the temporary holding centers it operates and that all treatment complied with international and U.S. laws.

Apart from Bagram prison, there are smaller jails on foreign military bases around Afghanistan where detainees are held before taken to Bagram or handed over to Afghan authorities.

Earlier this year, there were around 1,000 prisoners held in foreign military detention centers in Afghanistan, more than 800 of them in the main jail at Bagram.

Only recently have Afghan prisoners begun appearing before local judges and lawyers at Bagram jail, which the U.S. military says it is to start gradually handing over to the Afghans.