The US airbase at Bagram in Afghanistan contains a facility for detainees that is distinct from its main prison, the Red Cross has confirmed to the BBC.
Mirwais was watering his plants one night when American soldiers came to get him.
He is still missing half a row of teeth from the beating he says he got that night and he says he cannot hear properly in one ear.
US troops accused him of making bombs and giving the Taliban money.
Mirwais says he was taken to the 'black jail'.
In response to the allegations, Vice Admiral Robert Harward, in charge of US detentions in Afghanistan, denied the existence of such a facility or abuses.
He told the BBC that the Parwan Detention Facility was the only US detention centre in the country.
Hilary Andersson investigates detention at Bagram on BBC Radio 4 at 2002 BST (1902 GMT) on 11 May 2010