A second civilian investigation is being launched into the handling of prisoners in Afghanistan involving the Canadian military, the Military Police Complaints Commission said Monday.

The commission, an independent, quasi-judicial body of the federal government, said the second probe stemmed from a complaint filed by Amnesty International Canada and the British Columbia Civil Liberties Association on Feb. 21.

The complaint letter alleged that the Canadian Forces provost marshal and unidentified members of the Canadian Forces Military Police transferred detainees to Afghan authorities on at least 18 occasions even though there was evidence they would likely be tortured.

Commission chair Peter Tinsley cited the seriousness of the allegations as one of reasons to proceed with the second "public interest investigation." But he reserved a decision on whether to hold a public hearing into the matter.

"If our investigation uncovers evidence such that a public hearing would be warranted ... then I will exercise my authority to convene one," Tinsley said in a release.

Earlier this month, the commission launched the first "public interest investigation" into the way Canadian soldiers handled prisoners in the Afghan mission following a complaint filed by Amir Attaran, a law professor at the University of Ottawa. He based his complaint on military documents he requested under the Access to Information Act.

Attaran requested the complaints commission probe how at least one — and as many as three Afghan prisoners — were taken to military police by a single interrogator in one day in April 2006 with injuries to their faces, heads and upper bodies.

The military also launched its own investigation into Attaran's allegations.