It has been reported that the device found in a van in Co. Tyrone last night was viable.
Bomb disposal experts are still at the scene of the security alert in Aughnacloy.
The van was left outside the police station last night and the alarm was raised following a call to a Belfast newsroom.
Around 350 residents were evacuated from their homes and spent the night at a church hall.
Security sources say the device could have done untold damage.