Scotland has asked Libya's interim rulers to help find additional people who may have played a role in the 1988 bombing of a U.S.-bound jetliner that killed 270 people when it exploded over Lockerbie, Scotland.

Scottish authorities said Monday they have asked the National Transitional Council for written evidence and witnesses in the case.

Abdel Basset al-Megrahi has already been tried and convicted in Scotland for bombing Pan Am flight 103, and served eight years of a minimum 27-year sentence. He was freed in 2009 on compassionate grounds after a doctor said he had terminal cancer and only months to live.

Scottish authorities say Megrahi's trial found he had not acted alone, and that the investigation remains open.