The investigators, working with the FBI, are trying to determine whether a new case may be brought against Libyan suspects in the plot that crashed Pam Am Flight 103 in Lockerbie in 1988, killing 270 people, Edinburgh's Scotland on Sunday reported.
Police were unable to gain access to major suspects in Libya, Scotland on Sunday reported.
Crown Office investigators said they believe the only person convicted of the bombing, former Libyan intelligence officer Abelbaset Ali Mohmed al-Megrahi, did not act alone, but that the downing of the jetliner was, instead, "an act of state-sponsored terrorism."
While Scottish and U.S. authorities seek information on Al Amin Khalifa Fhimah, who was acquitted at his joint trial with al-Megrahi in Holland in 2001, as well as on other suspects, they say they believe Libyan officials are attempting protect members of the toppled regime, the newspaper reported.
"I think it was rather naive of us to think they would be given access," said former FBI assistant director Buck Revell, who directed the FBI's investigation until 1991.
"It was a long shot worth taking, given the magnitude of the tragedy, but people there are still protecting elements of the previous government. They don't believe it is in their best interests to come clean," he said.
Revell said western governments should use broad economic sanctions to get Libyan officials to cooperate.