LONDON – Scottish officials said Friday that police investigating the 1988 bombing of a U.S. jetliner over the town of Lockerbie have met with Libyan defector Mussa Kussa, who they believe has crucial information about Britain’s worst terrorist attack.

Prosecutors said in a statement that they would offer no additional details of their conversations with Kussa, Libya’s former spy chief and a close confidant of Moammar Gadhafi. But experts said Kussa could clear up lingering questions about the bombing of Pan Am Flight 103, which killed 270 people, most of them Americans.

Many of the victims’ relatives expressed cautious optimism about the interviews, which took place Thursday.

“I can’t imagine he’s going to implicate himself in the bombing, but he could give definitive evidence that Gadhafi is behind Lockerbie,” said Brian Flynn, a New York resident whose 21-year-old brother, J.P., was one of the victims.

“I think he is a potent source of information,” said Jim Swire, a British doctor who lost his 24-year-old daughter, Flora, in the attack. “But we should be extremely careful to interpret what he says,” said Swire, noting that Britain has repeatedly insisted that Kussa has not been offered immunity from prosecution.

Kussa, who was Libya’s intelligence chief for 15 years before becoming foreign minister in 2009, is the most senior official to defect from the Gadhafi regime since Libya’s uprising began in February. He has not been seen publicly since he arrived in Britain last week but reportedly is at a safe house.

Kussa is said to have played a vital role in the repatriation of Abdelbaset al-Megrahi, the only person convicted on charges relating to the Lockerbie bombing. Megrahi was released from a Scottish prison in 2009 on compassionate grounds after he was diagnosed with terminal cancer.

No one has ever claimed to have authorized the bombing, and conspiracy theories abound about who is responsible for the attack. The case remains open despite Megrahi’s conviction.

Jim Murdoch, a professor of public law at the University of Glasgow, said Scottish investigators will also be trying to uncover the nature of Kussa’s relationship with Megrahi and “the extent to which there is some form of criminal responsibility tied in with all of that.”

It is “improbable but not impossible” that Kussa could be convicted in a new trial, Murdoch said. “If he were to confess, the prosecution would still have to produce other evidence before a conviction is possible.”

Analysts say Kussa probably also has vital intelligence about other atrocities committed by Libya before it began repairing relations with the West in 2003.

Downplaying any revelations that might emerge, Gadhafi’s son Saif al-Islam told the BBC on Tuesday that Kussa was “sick and old” and prone to inventing “funny” stories about Lockerbie in hopes of securing immunity.

Britain’s foreign secretary described Kussa as “my channel of communication to the regime” in recent weeks, and he was reportedly instrumental in negotiations with Tony Blair’s government when Libya publicly disclosed and dismantled its weapons of mass destruction.