LONDON — Nearly 30 years after Pan Am Flight 103 exploded over the Scottish town of Lockerbie, investigators are still trying to crack the case of who exactly was behind the worst terrorist attack on British soil.

Scottish prosecutors said Thursday that they wanted to interview two Libyans who they suspect were involved along with Abdel Basset Ali al-Megrahi, the only person convicted in the 1988 bombing.

According to a U.S. official, who spoke on the condition of anonymity because of the ongoing investigation, the two suspects are Abdullah al-Senussi, former intelligence chief for ousted Libyan leader Moammar Gaddafi, and Abu Agila Mas’ud, an alleged bombmaker.

On Dec. 21, 1988, a bomb exploded on Pan Am Flight 103, which was traveling from London to New York. All 259 people on board, many of whom were Americans flying home for Christmas, were killed. Falling debris killed 11 people on the ground.

In a statement, Scotland’s Crown Office said Lord Advocate Frank Mulholland and U.S. Attorney General Loretta Lynch “have recently agreed that there is a proper basis in law in Scotland and the United States to entitle Scottish and US investigators to treat two Libyans as suspects in the continuing investigation into the bombing of flight Pan Am 103 over Lockerbie.”

The statement also said that Scotland and U.S. investigators want to interview the suspects in Libya, a country torn apart by fighting among various factions.

“We continue to seek more information, as well as access to those who might have been involved in the planning or execution of the bombing,” said Marc Raimondi, the Justice Department’s national security spokesman. He confirmed that Lynch and Mulholland met last month in Washington, but he said the department would not comment on "specific investigative steps that are being taken."

Prosecutors have always maintained that there were others involved with Megrahi, who was convicted in 2001 by a Scottish court set up in the Netherlands. He was sentenced to serve a minimum of 27 years but was freed amid controversy from a Scottish prison in 2009 after he was diagnosed with prostate cancer. Megrahi, who always maintained that he was not involved in the attack, died in Libya in 2012.

The announcement about the new suspects follows the airing of a three-part PBS "Frontline" series about Ken Dornstein's 25-year investigation into the case, which named potential suspects.

Dornstein’s older brother, David, was on the flight.

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