Homes have been evacuated in the Invernook Drive area of east Belfast after an explosion at a residential property.
The incident happened at 8.40pm on Friday.
The area has been cordoned off by police and army bomb experts are at the scene.
There are no reports of injuries after the blast, but local residents have been taken to a nearby hall until the area is declared safe.
Police have asked for anyone who witnessed suspicious activity in the area to come forward.
There are no further details at this time.
A lot of helicopter activity over east Belfast— Sharon O'Neill (@sharon_utv) March 9, 2012
A lot of helicopter activity over east Belfast
— Sharon O'Neill (@sharon_utv) March 9, 2012