The Federal Investigation Agency building in the Pakistani city of Lahore has been rocked by a bomb explosion.
Reports say the bomb was planted near a lift inside the building.
About 200 to 300 people are thought to work in the building.
The number of casualties is expected to rise. Violence across Pakistan has left more than 600 people dead this year.
This was one of two bombs to hit Lahore on Tuesday; the other explosion was in a residential area.
After the blasts, the Australian cricket team announced that their forthcoming tour of Pakistan had been cancelled over security fears.
Eyewitness reports said that fire was raging at the FIA building for some time after the explosion.
Pakistan's President Musharraf condemned the attacks, saying the government was determined to "fight the scourge" of terrorism.