Gardai are investigating whether there is a possible IRA link to a find of arms, ammunition and explosives on an isolated island.
The discovery was made on Nun's Island in Lough Ree, near Athlone in Co Westmeath by the landowner, who then notified gardai last night.
Army bomb experts were called in today after three suspect packages were spotted, which are believed to contain explosives.
A substantial quantity of ammunition and a smaller number of machine guns and rifles were also discovered hidden in a container on the island.
The explosives will be made safe by the Army Explosives and Ordinance Division before they are handed over to gardai to undergo forensic examination.
A Garda source said a link to the IRA was being investigated. He added there was no reason to believe locals were responsible for the arms dump, which may have been there for up to 15 years.
Nun's Island is one of a dozen uninhabited islands located in the middle of Lough Ree, one of the three major lakes on the River Shannon.
The owner of the island, Mr Ciaran O'Connor, had recently cut a lot of the overgrown trees and bushes in an attempt to make it more accessible.
In 1999 the Garda Water Unit began water patrols on the river Shannon. The then Garda Commissioner Pat Byrne warned about the possibility of sites on the river being used to store arms.