Scottish Justice Minister Kenny MacAskill said the "bulk" of the concern over the bomber of Pan Am flight 103 in 1988 is over whether British oil company BP landed an oil deal with the Libyan government in a prisoner exchange, London's Telegraph newspaper reports.
MacAskill in 2009 handed Abdelbaset al-Megrahi over to Libya because of health concerns, though a doctor said recently the Libyan could live for another 10 years.
British Prime Minister David Cameron during his visit to Washington this week said he was examining the details surrounding the 2009 prisoner transfer agreement but said the decision showed an error in judgment.
MacAskill said he had his own concerns about the link between accused bomber Megrahi and lucrative oil contracts in Libya.
"It was the British government that perhaps did a (oil) deal in the desert but that would be for them to state and for the senators to discover," he said.
U.S. officials are preparing their own probe into the deal with BP, which is already battered from the fallout from the Gulf of Mexico oil spill.
BP, which is to begin drilling off the coast of Libya later this year, admitted it was involved in talks on the prisoner exchange but said it wasn't involved directly with Megrahi.