A pipe bomb thrown at Strabane police station was viable, the PSNI has said.
The device, which failed to detonate, was discovered close to the perimeter fence after a telephone warning to the PSNI yesterday.
Army bomb disposal experts were called to the scene last night. A number of road closures were put in place and residents were urged to stay indoors.
It is understood the object had been thrown at the PSNI station at about 5pm on Wednesday and had lain undiscovered near a children's play park for 24 hours.
A spokeswoman for the PSNI said the bomb had the potential to cause serious injury or death.
PSNI Chief Inspector Andy Lemon said those who left the device were cowards.
"This is an extremely reckless act," he said. "It does not bear thinking about had a child picked it up. This is yet another example of the cowardly elements in our society who show no regard for local residents or the safety of police officers."
Last night ATO were continuing to work to make the bomb safe.