The suspect, Abu Agila Mohammad Masud, is currently being held by 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 newspaper said the exact location of Masud was unknown, but he was jailed in Libya at one point for crimes unrelated to him.
The Journal said Masud, believed to have been one of the late Libyan leader Muammar Gaddafi’s main bombmakers, is suspected of having assembled the device that blew up Pan Am Flight 103.
In 2003, Gaddafi accepted his country’s responsibility for the bombing and paid compensation to the families of the victims, but did not admit to personally ordering the attack.
Newspapers said US prosecutors are expected to disclose the charges against Masud soon.
32nd anniversary of the bombing
Monday is the 32nd anniversary of the bombing which killed a total of 270 people, including 190 Americans and 11 people on the ground.
To this day, the attack of December 21, 1988 remains the deadliest attack ever perpetrated by an extremist group on British soil.
The Journal said the case against Masud is largely based on a confession he made to Libyan authorities in 2012 as well as travel and immigration records.
In a statement, the FBI said that if it “cannot comment on any upcoming announcements, we can assure the public and, most importantly, the families of the victims of Pan Am 103, that we have worked tenaciously for 32 years to investigate about this horrific terrorist attack. “.
“Domestic and foreign partners have focused on identifying those responsible for the bombing,” the FBI said in a statement.
“As with any investigation, the FBI persists in our investigations by focusing on victims of crime and terrorism.”
Two Libyans were brought to justice in the Netherlands for their alleged role in the attack and one of them, Abdelbaset al-Megrahi, was sentenced in 2001.
Megrahi, a former Libyan intelligence officer, was sentenced to life in prison but was released in 2009 and died in 2012.
A Scottish court last month heard a posthumous appeal against his family’s conviction and the judges who heard the case are considering their decision.
Megrahi’s co-accused, Al Amin Khalifa Fimah, has been acquitted.
The outgoing United States Attorney General Bill Barr was the acting attorney general when the first charges were laid against Megrahi and the other Libyan official in 1991.