Afghanistan- US Forces interrogating Afghans in Aid Agency Compounds??

The Guardian was stirring things up last week with a series of articles predicting the collapse of Afghanistan along the lines of Iraq, all fueled by comments from OXFAM.

They did seed a rather explosive closing paragraph in the article, which really needs to be expanded:

'Separately, the Guardian has learned that, to the fury of civilian organisations, US forces are using an aid agency's property as a place to interrogate Afghans.'

The accusations seem a bit unlikely that these furious civilian aid agencies haven't already published multiple press releases on the subject... Hey, would be happy to be proven wrong, has anyone seem more details of these allegations?