Bomb disposal experts are examining a suspect device found under the car of a police officer in Belfast.
The security alert on the Upper Newtownards Road in the east of the city sparked the evacuation of a number of homes.
Army technical officers were working to establish if the device is a viable bomb.
SDLP Policing Board member Conall McDevitt condemned the apparent bid to target the officer.
"This is a cynical and deplorable act," he said.
"Those seeking to target police officers are undermining not only the stated will of the people of Ireland who have long since rejected violence, but also the desire for a new beginning for policing in the North, which is shared by the majority of citizens."
The Stormont Presbyterian Church has opened to accommodate residents who have had to leave their homes during the alert.