WASHINGTON — The Justice Department announced new charges Monday against a Libyan bombmaker in the 1988 explosion of Pan Am Flight 103 over Lockerbie, Scotland, an attack that killed 259 people in the air and 11 on the ground.

The charges were announced on the 32nd anniversary of the bombing and in the final news conference of Attorney General William Barr’s tenure.

He had announced an earlier set of charges against two other Libyan intelligence officials in his capacity as acting attorney general nearly 30 years ago, vowing that the investigation would continue.

The case against the alleged bombmaker, Abu Agela Masud Kheir Al-Marimi, is for now more theoretical than practical since Masud is not in U.S. custody.

A breakthrough in the investigation came when U.S. officials in 2017 received a copy of an interview that Masud, an explosives expert for Libya’s intelligence service, had given to Libyan law enforcement several years earlier after being taken into custody following the collapse of the regime of the country’s leader, Col.

Moammar Gadhafi.

In that interview, U.S. officials said, Masud admitted building the bomb in the Pan Am attack and working with the two other defendants to carry it out.

While Masud is now the third Libyan intelligence official charged in the U.S. in connection with the Lockerbie bombing, he would be the first to stand trial in an American courtroom.

The Pan Am flight exploded over Lockerbie lessthananhouraftertakeoff from London on Dec. 21, 1988, en route to New York City and then Detroit. I