A pipe bomb has exploded in the Millar's Forge area of Dundonald.
Police were called to reports of the explosion at 1.05am on Thursday morning, where the device was found in a garden.
Army Technical Officers examined the object and confirmed it to be a viable pipe bomb type device that had detonated.
No one was injured by the blast but slight damage was caused to a parked car.
The security alert ended at around 6am.
Detectives in Castlereagh are appealing for anyone who noticed unusual activity in the area to contact CID on 0845 600 8000, or Crimestoppers on 0800 555 111.