Some relatives of victims of the bombing want to see an inquiry
The families of the victims of the Lockerbie bombing have welcomed moves by police in Scotland to pursue "several potential lines of inquiry".
However, they renewed calls for a public inquiry into the 1988 atrocity.
The fresh police probe comes after the only man convicted of the atrocity, Abdelbasset al-Megrahi, dropped his appeal before he was returned to Libya.
Prosecutors said Megrahi, who was freed in August on compassionate grounds, had not worked alone.
Pan Am flight 103 from London to New York exploded over the Scottish town of Lockerbie on 21 December 1988, resulting in the death of 270 people.
Libyan Megrahi, who has inoperable prostate cancer, was convicted of the bombing in 2001 and served eight years in prison before being released in August.
Days before his release Megrahi, who has always protested his innocence, dropped his second appeal against conviction.
The Crown Office - Scotland's prosecuting authority - told relatives of British victims, via e-mail, that a police review of the case had started now that "appeal proceedings were at an end".
It said police were following several new lines of inquiry, including a review of forensic evidence into the 1988 bombing.
The chief constable of Dumfries and Galloway, Patrick Shearer a further review of the case was under way "in respect of others who acted with Megrahi in the murder of 270 people".
Mr Shearer said: "The work that is being undertaken is the latest in a series of reviews which have formed part of an investigative strategy in keeping with our determination to pursue every possible lead.
"We also take cognisance of the trial court's acceptance of Crown's position that Mr Megrahi acted in furtherance of the Libyan Intelligence Service and did not act alone."
Pamela Dix, who lost her brother, says a public inquiry should also be held
The victims' families are keen to bring to light evidence which was likely to have emerged in Megrahi's now-abandoned appeal case.
They have urged investigators to make the renewed probe "meaningful".
Members of campaign group UK Families Flight 103 delivered a letter to the UK prime minister asking for a full independent inquiry, and requesting a meeting with him.
Pamela Dix, whose brother Peter was killed in the bombing, said the announcement of the police review should be interpreted as a "good thing" but should not be used to replace a full public inquiry.
"Expectations around Megrahi's appeal were really quite high but hopes were profoundly dashed when the appeal was abandoned. The situation is unresolved and it is unfinished business," she said.
She added: "We do not know what the motivation for the bombing was, who ordered it, why was it carried out, how was it allowed to happen with the amount of information that the intelligence services had... concerning threats against American aviation.
"So not only do we not know what was the ultimate motivation for the bombing... but we know really very little about what was actively done to try and prevent [it]."
Megrahi was convicted of the Lockerbie bombing in 2001
Dr Jim Swire, who has campaigned for a full inquiry into the bombing since his daughter Flora died in the atrocity, said: "I think that if they are really going to a meaningful investigation then that is all well and good and long overdue.
"But if it is just a dodge to prevent an investigation into why the lives of those killed were not protected then I would be livid."
UK Foreign Secretary David Miliband told the BBC's Andrew Marr programme a public inquiry was an issue for the Scottish government.
He said: "We have always said that this was something that happened over Scottish soil, it was investigated by the Scottish authorities, it is right that they pursue the investigation on a criminal basis and if there is any suggestion of an inquiry that should be a matter for the Scots, because that's the way our system works."
A Scottish government statement said it would welcome a wide-ranging inquiry into the circumstances of the Lockerbie atrocity but it did not have the powers to hold it.
It said: "Given the international dimensions to this issue, the remit of any such inquiry goes well beyond the restricted remit and responsibilities of the Scottish government or Scottish Parliament, and would therefore have to be convened by those with the required powers.
Scots should decide on Lockerbie
"Scottish authorities would cooperate in full in any such inquiry, and our police and prosecution services have done an excellent job throughout the Lockerbie investigation."
Richard Marquise, who was the FBI's lead investigator in the original inquiry, said he was "hopeful" that new evidence could be found but it might be a long and laborious process.
He said that the political structure of the world had changed since 1988 and some foreign governments may now be able to offer more help.
Mr Marquise added: "Mr Megrahi did not do this alone, it was ordered from above. There probably were people that worked with him, people that were involved in the bombing effort itself.
"We always hoped that those people, their names would become clearer and they could be identified and eventually prosecuted. Thus far that hasn't happened."
Dr Adrian Linacre, a senior lecturer in forensic science at Strathclyde University, said there had been "great advances" in DNA-typing in the 21 years since the bombing.
He said investigators would look at items people had held or touched.
But he said it would be "quite an achievement" to find DNA on fragments of the bomb due to the impact of the explosion and the passage of time.
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