A US Senator investigating the 2009 release of the Lockerbie bomber has asked whistleblowers to step forward.
Sen Robert Menendez issued a public plea for people with inside knowledge of talks between BP and Libyan and British authorities to speak up.
Some US lawmakers suspect that BP had lobbied for the bomber's release, suggesting that it aided the energy giant's oil exploration in Libya.
The inquiry comes amid US anger over the BP oil spill in Louisiana.
Assuring confidentiality for sources, Mr Menendez asked also for behind-the-scenes information regarding Abdelbaset Ali al-Megrahi's medical condition.
Scottish authorities released Megrahi in August 2009 on compassionate grounds, citing terminal cancer which had left him just three months to live. Megrahi is still alive almost a year later.
The Scottish government has denied that it was under pressure from BP to release Megrahi and has defended the medical assessments of his condition.
The 1988 Lockerbie bombing killed 270 people, including 189 Americans.