Scottish and US authorities informed Libya they want to send investigators to Libya, which is wracked by civil war, to interview the new suspects, the office of Scotland's chief prosecutor said.
Marc Raimondi, a US Justice Department spokesman, said US Attorney General Loretta Lynch and chief Scottish prosecutor Frank Mulholland met in Washington last month to discuss the investigation.
Pam Am flight 103 was blown up over the Scottish town of Lockerbie on Dec. 21, 1988 en route from London to New York. In 2001, Libyan Abdel Basset al-Megrahi was jailed for life and remains the only person to have been convicted over the bombing.
A second Libyan accused of involvement, Lamin Fhima, was tried with Megrahi before a panel of Scottish judges sitting at a special court in the Netherlands but was found not guilty.
A Scottish Crown Office spokesman said two Libyans who were not named are now suspected of being involved with Megrahi in carrying out the attack.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
Scotland's chief prosecutor, known as the Lord Advocate, "has today ... issued an International Letter of Request to the Libyan Attorney General in Tripoli which identifies the two Libyans as suspects in the bombing of flight Pan Am 103," the spokesman said.
"The Lord Advocate and the US Attorney General are seeking the assistance of the Libyan judicial authorities for Scottish police officers and the FBI to interview the two named suspects in Tripoli."
In 2003, former Libyan leader Muammar Gaddafi accepted his country's responsibility for the bombing and paid compensation to the victims' families, but he did not admit personally ordering the attack.
Megrahi, who protested his innocence, died in Libya in 2012. He was released three years earlier by Scotland's government on compassionate grounds after being diagnosed with terminal cancer. His family and some relatives of the Scottish victims believe he was wrongly convicted.
In December, Scotland's top prosecutor said no new evidence had emerged to cast doubt on Megrahi's conviction but attempts to track down accomplices had been hampered by the violence in Libya since Gaddafi's fall.
Jim Kreindler, a lawyer for families of PanAm 103 victims said: "I think its important for history to record exactly who else was involved with Megrahi."
(Reporting by Michael Holden in London and Mark Hosenball in Washington; editing by Kate Holton and Hugh Lawson)
