Hillary Clinton, the US Secretary of State, is to look into suspicions raised by American senators that oil giant BP was part of a deal to free the man convicted of the Lockerbie bombing in return for Libyan oil.
The four senators from New York and New Jersey, states that were home to many of the 189 American victims of the UK's worst terrorist atrocity, want the company to halt its planned drilling in Libyan waters while an investigation takes place.
The BP deal with Tripoli, worth £590 million, was sealed in 2007 after Abdelbaset Ali Mohmed al Megrahi was unexpectedly added to a prisoner transfer agreement between the UK and Libya.
Last August, Kenny MacAskill, Scotland's Justice Secretary, freed Megrahi on compassionate grounds because of medical advice that the 57-year-old cancer sufferer might have only three months to live.
At the time and ever since, MacAskill has strenuously maintained his decision had nothing to do with the transfer agreement or any oil deal.
However, suspicions have been raised in the US after Professor Karol Sikora, a cancer specialist paid by Libya to diagnose Megrahi, admitted the convicted terrorist could live for another 10 years.
Yesterday, The Herald exclusively revealed the Libyan was not responding to chemotherapy, with experts saying "a cold could finish him off".
The senators had called for the UK Government to investigate their suspicions, but have been rebuffed by Whitehall.
The Foreign Office is likely to be extremely concerned that the BP scandal in America over the Gulf of Mexico oil disaster is now being tied up with the lasting controversy surrounding Megrahi and the Scottish Justice Secretary's contentious decision to free him.
On Tuesday, the senators wrote to the US Secretary calling for a Washington inquiry into BP's alleged role in the release.
Clinton said yesterday: "I have received the letter and we will obviously look into it."
Last night, one of the senators, Robert Menendez, a Democrat who represents New Jersey, said: "The more we learn about the release in recent days, the more it makes the stomach turn."
"If BP is found to have gained access to Libyan oil reserves by using a mass murderer as a bargaining chip then, make no mistake, any money it makes off of that oil is blood money."
Senator Chuck Schumer from New York noted: "If it walks like a duck and quacks like a duck, then it just might be a corrupt deal between BP, the British Government and Libya."
Some 270 people died in the 1988 bombing of Pan Am Flight 103 over Lockerbie.