The United States plans to unseal charges soon against a Libyan man suspected of assembling the bomb that blew up a US airliner over Lockerbie, Scotland, in 1988, US newspapers reported on Wednesday.
The suspect, Abu Agila Mohammad Masud, is currently held by the Libyan authorities, according to The Wall Street Journal, and US authorities are seeking his extradition to stand trial in the United States.
The New York Times said Masud's exact whereabouts are unknown but he was imprisoned in Libya at one point for unrelated crimes.
The Journal said Masud, alleged to have been a top bomb-maker for the late Libyan leader Muammar Ghaddafi, is suspected of assembling the device that blew up Pan Am Flight 103.
The newspapers said US prosecutors are expected to unseal charges soon against Masud.
Monday is the 32nd anniversary of the bombing which killed a total of 270 people, including 190 Americans and 11 people on the ground.
The Journal said the case against Masud is based largely on a confession he gave to Libyan authorities in 2012 as well as travel and immigration records.
In a statement, the FBI said that while it "cannot comment on any upcoming announcement, we can assure the public and most importantly, the families of the Pan Am 103 victims, that we have worked tenaciously for 32 years to investigate this horrific terrorist attack."
"Domestic and foreign partners alike have been focused on identifying who was responsible for the bombing," the FBI said in a statement. "Just as in any investigation, the FBI is persistent in our investigations with a dedicated focus on the victims of crime and terrorism."
Two Libyans were put on trial in the Netherlands for their alleged roles in the attack and one of them, Abdelbaset Mohmet Al-Megrahi, was convicted in 2001.
Megrahi, a former Libyan intelligence officer, was sentenced to life in prison but was released in 2009 and died in 2012.
A court in Scotland last month heard a posthumous appeal against his conviction brought by his family and the judges who heard the case are mulling their ruling.
The outgoing US attorney general, Bill Barr, was the acting attorney general when the first charges were brought against Megrahi and the other Libyan official in 1991.