Gardai expect to find more IRA weapons and explosives as they follow up information they have received since the murder of Det Garda Jerry McCabe.
Last night, detectives were examining explosives, bomb making equipment and guns from a 14 ft by 6 ft bunker, under the farmhouse in Clonaslee, Co Laois, where they earlier found an IRA bomb factory.
Garda technical officers examining the house yesterday uncovered the entrance to the bunker in the front garden. A tunnel led to the bunker where, it is understood, they found Semtex and home made explosive, mortars, detonators, electrical bomb components and firearms including a general purpose machinegun.
According to one source, there may be more than two tons of equipment and explosives in the bunker. Among the equipment examined were up to 20 timer power units, used to detonate bombs as well as "initiators" to fire mortars.
Four men, two from Dublin and two from the Midlands, were still being questioned by gardai last night. Two were being questioned at Santry Garda Station and two at Portlaoise.
One of the men arrested, who is formerly from Northern Ireland but is now living in Dublin, has been described as the head of the IRA's "Southern Command".
Another of those held was suspected of being central to the IRA gun running operation from Libya between 1985 and 1987 but was never charged. He is also said to be one of the organisation's top bomb makers.
The four were arrested on Thursday night under Section 30 of the Offences Against the State Act and can be held until this evening without charge.
Yesterday, gardai said they have received "very significant" information, leading to the arms caches, as a result of their inquiries into the murder of Det McCabe, in Adare, Co Limerick, 15 days ago.
The sources said the information is expected to lead to more seizures and arrests in the coming days.
Yesterday, gardai concentrated their main forensic and ballistic examinations on the bunker under the house at Ballyfarrell, Clonaslee, which was opened in the afternoon.
It is believed that the gardai will concentrate their attention today on an industrial unit in the Ballymount Industrial Estate, at Walkinstown, Dublin. The unit is rented by one of the arrested men and was seized and sealed off by Special Branch officers on Thursday night.
The premises was examined for fingerprints and other evidence yesterday and a fuller search for hidden arms and explosives is expected today.
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