Lockerbie bombing: 'Useful' talks held with FBI
Scotland's top law officer has met the director of the FBI to discuss progress in the investigation into the Lockerbie bombing.
Lord Advocate Frank Mulholland QC described Friday's talks with James Comey as "very useful".
Mr Mulholland also revealed he recently met the Libyan ambassador to the UK.
Relatives of the 270 people who died have attended a memorial service in Washington to mark the 26th anniversary of the atrocity.
The Lord Advocate was among a delegation of Scottish law officers who also travelled to the Arlington cemetery for Sunday's service.
On Saturday, Mr Mulholland said he continued to believe Abdelbaset al-Megrahi was guilty of carrying out the bombing, and pledged to continue tracking down his accomplices.
Megrahi who was said to have been a Libyan intelligence officer, is the only person to have been convicted over the bombing, which caused Pan Am flight 103 to explode over Lockerbie, in the south of Scotland, on 21 December 1988.
But his involvement in the bombing of the flight from London to New York has been called into question by campaigners who believe evidence in the case was manipulated to implicate Libya and divert attention away from Iran and Syria.
In a speech at the memorial service, Mr Mulholland said his commitment to the ongoing investigation remained "as strong as ever".
And he urged relatives of those who died not to give up hope that others will eventually be brought to justice.
He said: "To reinforce that message, I met last week with the Libyan ambassador to the UK.
"He asked me to reassure you that his thoughts are with you at this difficult time and reiterated the commitment of the Libyan authorities to work with us to gather the evidence from Libya to bring the others who worked with Megrahi in the murder of your loved ones to justice."
The Lord Advocate said he was also keeping in close contact with the UK ambassador to Libya, who is currently based in Tunis, to get regular updates on what is happening.
The ambassador has been "able to get information for us which has been helpful in shaping our approach going forward." Mr Mulholland said.
Turning his attention to work with officials in the US, the Lord Advocate added: "I met with Director Comey of the FBI on Friday to discuss progress in the inquiry. It was a very useful meeting and the avenues of enquiry currently under investigation were discussed in detail.
"Despite the difficulties we remain hopeful that progress will be made. We reiterated our commitment to work closely together to make progress in Libya and elsewhere; wherever there is an opportunity we will be there. We will follow the evidence relentlessly."
Details of the ongoing investigation have not and will not be made public, the Lord Advocate said.
But he added: "What I can say however is that in addition to the lines of enquiry in Libya there are other lines currently being pursued outwith Libya.
"We remain cautiously optimistic that these lines of enquiry will bear fruit."
Megrahi was found guilty of mass murder by a Scottish court sitting in the Netherlands in January 2001. His co-accused Al Amin Khalifa Fhimah was acquitted.
Megrahi was jailed for life and lost his first appeal against his conviction for murdering the 259 people on the plane and 11 Lockerbie residents in 2002.
An investigation by the Scottish Criminal Cases Review Commission (SCCRC) led to a finding in 2007 of six grounds where it believed a miscarriage of justice may have occurred, paving the way for a second appeal.
But Megrahi dropped that appeal in 2009 before being released from prison by the Scottish government on compassionate grounds in light of his diagnosis with terminal prostate cancer.
He died, still protesting his innocence, in Libya in 2012.
Mr Mulholland said on Saturday that no Crown Office investigator or prosecutor had ever raised any concerns about the evidence used in the case.
But earlier this year, Megrahi's relatives embarked on a legal bid to clear his name amid claims that his case is the "worst miscarriage of justice in British legal history".
Six immediate members of his family joined forces with 24 British relatives of those who died in the atrocity to seek, ultimately, a third appeal against his conviction in the Scottish courts.
They united to submit an application to the SCCRC for a review of the conviction, a move which could see the case referred back to the High Court.
Solicitor Aamer Anwar, who is co-ordinating efforts to quash Mr Megrahi's conviction, said: "The Lord Advocate's speech in Washington makes for great sound bites with an American audience but lacks analysis of the essential facts."
He accused the Crown Office of repeating "an age old mantra of the Crown of never doubting the safety of the conviction", despite "many miscarriages of justice over the years".
Mr Anwar added: "The case of Abdelbaset Al-Megrahi is described as the worst miscarriage of justice in British legal history for a reason.
"A reversal of the verdict would mean that the governments of the United States and the United Kingdom stand exposed as having lived a monumental lie for 26 years, by imprisoning a man they knew to be innocent."
In a statement, the Megrahi family said it would "keep fighting for justice to find out who was responsible for 271 victims of the Lockerbie disaster."
Jim Swire, whose 23-year-old daughter Flora died in the bombing, has also expressed his disappointment at Mr Mulholland's latest comments.
Dr Swire said: "For me this case is about two families, mine and Abdelbaset's, but behind them now are seen to lie the needs of 25 other families in applying for a further appeal 26 years after the event itself.
"We need the truth and Scotland's management of this case produced a verdict perfectly tailored for use by those who would seek to ensure that the full truth remains hidden."