The US is due to unseal charges against a Libyan man suspected of making the bomb that blew up Pan Am Flight 103 over Lockerbie in 1988, US media say.
US prosecutors will soon seek the extradition of Abu Agila Mohammad Masud to stand trial in the US, reports say.
He is currently being held in Libya, according to the Wall Street Journal. This has not been confirmed by the Libyan authorities.
The blast on board a Boeing 747 over the Scottish town left 270 people dead.
Most of the victims on board the flight from London to New York were American citizens.
It remains the deadliest terrorist incident ever to have taken place on British soil.
Libyan national Abdelbaset al-Megrahi was the only man convicted, in 2001, over the bombing.
Megrahi, who always proclaimed his innocence, unsuccessfully appealed against his 27-year sentence.
However, he was released from prison in Scotland and allowed to return to Libya on compassionate grounds in 2009 after it emerged that he had terminal cancer.
Megrahi died three years later, but a Scottish court is now considering a posthumous appeal against his conviction by his family.
What are US media reporting?
The US Department of Justice is expected to unseal a criminal complaint against Abu Agila Mohammad Masud in the coming days, the Wall Street Journal is reporting quoting senior department officials.
It says this will open a new chapter in one of the world’s longest and most sprawling terrorism investigations.
The new charges are expected to be announced by outgoing US attorney-general, William Barr.
He held the same position when the US announced its first charges against Megrahi and another Libyan suspect, later acquitted, almost three decades ago.
“We will not rest until all those responsible are brought to justice. We have no higher priority,” Mr Barr said at the time.
The Wall Street Journal reports that Mr Masud is being held in Libya, although the New York Times says his exact whereabouts are unknown. But it adds that he was jailed in Libya at one point for unrelated crimes.
Mr Masud is alleged to have been a top bomb-maker for late Libyan dictator Muammar Gaddafi.
Neither the US justice department nor the Libyan authorities have publicly commented on the issue.
Lockerbie bombing – timeline
US and British investigators indicted Megrahi in 1991 but he was not handed over by the Libyans until April 1999.
May 2000 – A special trial under Scots law starts on neutral ground at Camp Zeist in the Netherlands.
31 January 2001 – Former Libyan intelligence officer Megrahi is found guilty of mass murder and jailed for life with a minimum term of 27 years.
March 2002 – Megrahi loses an appeal against his conviction.
September 2003 – The Scottish Criminal Cases Review Commission (SCCRC) is asked to investigate Megrahi’s conviction.
June 2007 – The SCCRC recommends that Megrahi is granted a second appeal against his conviction.
18 August 2009 – Megrahi’s move to drop his second appeal is accepted by judges at The High Court in Edinburgh.
20 August 2009 – Megrahi, who has terminal prostate cancer, is released from prison on compassionate grounds.
May 2012 – Megrahi dies at his home in Tripoli, aged 60.
July 2015 – Scottish judges rule that relatives of the Lockerbie bombing victims should not be allowed to pursue an appeal on Megrahi’s behalf. Courts had previously ruled that only next of kin could proceed with a posthumous application.
July 2017 – Megrahi’s family launched a new bid to appeal against his conviction.
March 2020 – The Scottish Criminal Case Review Commission said Megrahi’s conviction can be taken to a fresh appeal.
November 2020 – Five Scottish judges hear the third appeal against Megrahi’s conviction on grounds of possible miscarriage of justice