The building was badly damaged in the explosion and some vehicles parked outside the building were totally destroyed.
There were more than two hundred people working inside the seven-story building at the time of the blast.
An official of a rescue team was quoted as saying that at least 18 people including 10 FIA employees were killed and around 100 others were injured.
Two explosions took place in eastern Pakistan on Tuesday morning, killing at least 20 people, local TV channel DAWN NEWS reported.(Xinhua Photo)