Detonators recovered as part of an arms and explosives find in west Belfast earlier this week appear to be of "1998 manufacture", the RUC said last night.
This has led to claims from the UK Unionist Party leader, Mr Robert McCartney, and the Northern Ireland Unionist Party that the IRA has breached its ceasefire, which started in 1997.
The RUC has said the discovery is the "most significant" in west Belfast in the past two years, and that the arms and explosives found at St Catherine's Road off the Falls Road belonged to the IRA.
The haul, which was uncovered on Tuesday, included an Armalite rifle, four pounds of home-made explosives, coffee-jar bombs, commercial detonators and hundreds of rounds of ammunition.
The RUC spokeswoman said that the rifle was "old." The arms and explosives were undergoing forensic testing.
Mr McCartney said the evidence that the detonators were made after the July 1997 ceasefire repudiated the existence of a bona- fide IRA cessation. "Far from intending to decommission, the IRA has in fact been rearming during its ceasefire, and during the period when David Trimble was negotiating with them," he said.
"No ceasefire could be regarded as intact if a paramilitary organisation is using it to import new weapons. Not even Mo Mowlam could have the brass neck to claim in the light of this new evidence that the IRA ceasefire is real," he added.
The discovery highlighted the folly of the UUP leader, Mr Trimble, even contemplating sitting on an executive with Sinn Fein, Mr McCartney said.
The Northern Ireland Unionist Party - which recently broke away from the UKUP - met the Northern Security Minister, Mr Adam Ingram, to press for a clear declaration on the British government's attitude to decommissioning. Mr Paddy Roche, one of the party's four Assembly members, said the arms find constituted a breach of the ceasefire.
A Sinn Fein spokesman said last night that he would not comment on "speculative claims" from the "dubious" RUC and from politicians "who are intent on wrecking the peace process".
