Actually, it was in Dick Cheney's suite of offices.
Quick response from the DC Fire Department (the world's finest) limited this fire to smoke and water damage in Cheney's offices, and kept the fire from spreading to other offices. The only injury was to a U.S. Marine stationed at the offices, who had to break a window on the 5th floor of the building to escape and cut his hand in the process. He was rescued from the building's ledge.
The cause of the fire is unknown at this time.