Irish police are continuing to examine the scene in County Donegal where ex-Sinn Fein official and British agent Denis Donaldson was murdered.
Members of the Gardai's water and dog units are taking part in the search.
Post mortem results indicated Mr Donaldson died from a shotgun wound to the chest, said police.
Other injuries to his body were consistent with shotgun blasts, including a severe injury to his right hand, according to the post mortem.
Police removed a car at the scene for further examination on Thursday.
The IRA has denied involvement in the murder of the ex-Sinn Fein man.
He was found shot dead following a break-in at a remote cottage near the village of Glenties, County Donegal, on Tuesday.
He had been expelled from Sinn Fein in 2005 after admitting he was a paid British spy.
On Wednesday, Irish Premier Bertie Ahern said Mr Donaldson was warned that his life could be in danger.
He said police became aware of his whereabouts in January, but he did not request any protection.
TIMETABLE OF EVENTS
4 October 2002: Three men including Mr Donaldson arrested following raid on Sinn Fein's Stormont office. Power-sharing executive collapses and government restores direct rule to NI a week later
8 December 2005: Charges against three men dropped "in the public interest"
16 December 2005: Sinn Fein says Mr Donaldson was a "British agent" and expels him from the party: he later says he worked as a spy since the 1980s
Government and police reject the party's claim raid was politically motivated
4 April 2006: Mr Donaldson found shot dead in County Donegal
NI Secretary Peter Hain said on Thursday that suggestions British intelligence were behind Mr Donaldson's murder were "fanciful and rather desperate".
He said it was more likely that dissident republicans carried out the shooting.
At a news conference in Donegal on Wednesday, Chief Superintendent Terry McGinn refused to be drawn on details of the killing, or on whether there had been a specific threat to Mr Donaldson.
She said the door had been forced and a window broken in the property. She added they were keeping an open mind about the inquiry.
Mr Donaldson's death came ahead of Thursday's visit to Northern Ireland by Tony Blair and Mr Ahern to unveil their blueprint for reviving the assembly at Stormont.
The British and Irish prime ministers insisted they would not let the murder derail the political process.
Mr Donaldson moved out of his Belfast home last December, and had been living in the run-down cottage which had neither electricity nor running water.
He had been Sinn Fein's head of administration at Stormont before his 2002 arrest over alleged spying led to its collapse.
Charges against him and two others were dropped last December "in the public interest".
One week later he admitted being recruited in the 1980s as a paid British agent.
He said there had not been a republican spy ring at Stormont.