TESTS are continuing today as police try to find the killer of former Sinn Fein chief turned spy Denis Donaldson.
Police in the Irish Republic are examining a remote cottage near Glenties in County Donegal where 56-year-old Mr Donaldson was shot dead yesterday.
The Provisional IRA has denied any involvement in the killing.
Meanwhile, Prime Minister Tony Blair and Irish Taoiseach Bertie Ahern were insistent that they would go ahead with visits to Northern Ireland tomorrow, despite the murder.
Mr Donaldson, Sinn Fein's former head of administration at Stormont - who was unmasked by party leader Gerry Adams as a British spy last December - had been living in the cottage with no electricity or mains water after being ostracised by former republican comrades.
His brutal murder sent shockwaves throughout republicanism and the wider political circles in Northern Ireland.
But it also intensified unionist scepticism about Mr Blair and Mr Ahern's efforts to revive a power-sharing executive.
Democratic Unionist MP Sammy Wilson said the Provisional IRA would be regarded by unionists as the chief suspects, even if there was no absolute proof of the group's involvement.
Meanwhile, Mr Blair and Mr Ahern intend to recall the Northern Ireland Assembly in May, in a bid to form a power-sharing executive featuring the DUP and Sinn Fein by the summer.
But if, as most people expect, that proves impossible, officials will put the political process on hold through the summer and resume efforts in September.
They will then give the Northern Ireland Assembly a deadline of November 24 to form the executive.
But unionists and nationalists were dubious about the prospects of devolved government even before yesterday's murder.