(CNN) -- The Senate Foreign Relations Committee has invited BP Chief Executive Tony Hayward to answer questions next week about BP and the release of the convicted Lockerbie bomber, a congressional source told CNN Wednesday.
Four senators have said that questions need to be answered over how Abdelbaset Ali Mohmed al Megrahi, described as terminally ill, could have survived almost a year and whether BP exerted influence in the case.
The Scottish government has insisted that BP never lobbied to free al Megrahi.
The senators, who met Tuesday with Prime Minister David Cameron, said the British leader could still call for an independent investigation of last year's release by Scotland of al Megrahi, convicted in the 1988 Lockerbie bombing that killed 270 people.
Al Megrahi was convicted in the case and sentenced to life in prison. The Scottish government released him on compassionate grounds last August after doctors said he had terminal prostate cancer and just three months to live.
Al Megrahi is still alive, and news reports in recent days have questioned whether he was as sick as depicted. Questions also have been raised about whether a deal was cut to release him to protect British business interests in Libya, possibly involving BP.
Cameron promised that the British government will cooperate with a U.S. congressional investigation into the controversy, though he stressed that the decision to release al Megrahi was made by the Scottish government without any involvement from BP.