Rescue teams are looking for survivors in the building and the injured are being sent to local hospitals.
Local media reported that 11 suspects were being questioned in the FIA building when the blast occurred.
The other bomb blast ripped through a building in Model Town in Lahore shortly after the FIA blast. Four people were feared killed and three others were injured.
The front of the building at a house in Model Town, which served as the office of an advertising agency, was totally destroyed in the explosion.
Two suicide bombers managed to enter the house and blew themselves up, killing two children in the house.
Police and Rescue teams have reached the spot and have started rescue operations.
Pakistani President Pervez Musharraf and caretaker Prime Minister Mohammadmian Soomro strongly condemned the twin blasts in Lahore.
Two explosions took place in eastern Pakistan on Tuesday morning, killing at least 20 people, local TV channel DAWN NEWS reported. (Xinhua Photo)
(Xinhua News Agency March 11, 2008)
