Al-Megrahi maintains that he is innocent but he dropped an appeal against his conviction prior to his release in August.

'Further review'

"Now that Mr Megrahi has decided to abandon his appeal against conviction, a further review of the case is under way in respect of others who acted with him in the murder of 270 people," Patrick Shearer, the chief of Dumfries and Galloway police, said.

In depth

 Profile: Abdel Basset al-Megrahi
 Bomber's homecoming slammed
 Release prompts anger and relief
  Video: Al-Megrahi speaks out
  Video: Opinions divided over Lockerbie appeal
 Video: Lockerbie remembered
 Al-Megrahi statement in full

"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."

Scotland's prosecuting authority, the Crown Office, said the review does not include the question of al-Megrahi's involvement.

"There is no question of re-opening the case against [al-Megrahi]," it said in a statement.

"The open case concerns only the involvement of others with [al-Megrahi] in the murder of 270 people and the Crown will continue to pursue such lines of inquiry that become available."

Al-Megrahi, who is in hospital in Tripoli, Libya's capital, had been serving a 27-year-sentence for planting a bomb on Pan Am Flight 103, which exploded over Lockerbie in 1988.

Scotland's decision to release him sparked anger in Britain and the US from officials and relatives of victims, who say he should have remained behind bars.

The former Libyan intelligence agent, who was sentence by a specially convened Scottish Court in The Netherlands in 2001, has always proclaimed his innocence.

His Scottish lawyers also argued he was the victim of a miscarriage of justice.