A 33-year-old man has been arrested as part of the investigation into the discovery of a viable device in Strabane, Co Tyrone, at the weekend.
The device was found in the Church View area.
Police believe a pizza delivery car - an orange Fiat Sedici - was hijacked in the area of Mount Sion, Ballycolman at around 9.40pm on Friday and driven to Church View where the device was left.
The car was then abandoned on Evish Road in the town.
The device was found on Saturday morning and a number of homes had to be evacuated as part of a security alert.
The man was arrested yesterday in the Strabane area and remains in custody.
Police believe the device was targeted at PSNI officers and that the New IRA was "responsible for the mortar device".