OTTAWA - Newly obtained documents show Canada's spy service admits interrogating up to 50 Afghan prisoners captured by the Canadian Forces.

But the Canadian Security Intelligence Service documents insists they were never mistreated.

The CSIS involvement in interviewing suspected Taliban fighters alongside military intelligence officers was revealed by The Canadian Press last March.

But details of the agency's role and actions have remained largely cloaked in secrecy.

Briefing notes prepared for CSIS director Dick Fadden take pains to emphasize the conduct of agents has been above reproach.

University of Ottawa law professor Errol Mendes wonders whether spies travelled along with soldiers in combat, saying that may exceed the legislated mandate of CSIS.

The documents, obtained by The Canadian Press under the Access to Information Act, were drawn up to brief Fadden for a June interview with the CBC, but the broadcaster did not ask him about CSIS's role in Afghanistan.