Eighty P.S.N.I. officers and explosive detection dogs are conducting searches for dissident republican bomb-making equipment in a Northern Ireland housing estate.
Specialist search officers and neighbourhood officers took part in the searches in the Creggan estate in Londonderry on Monday morning.
Superintendent Gordon McCalmont confirmed the details of the searches during a press conference at Strand Road P.S.N.I. Station.
The searches are in connection with a failed mortar bomb attack in Strabane, Co. Tyrone at the weekend.
The P.S.N.I. believe the group calling itself the 'New I.R.A.' were responsible for the attack.
"Our assessment is that this group is concealing bomb-making materials in this area [Creggan]
"We have a number of areas of focus, however there is no definitive and no guarantees.
"However, our chances are improved by support and information from the community," said Superintendent McCalmont.