An explosion went off in Olso's government headquarters early Friday, injuring several people. Prime Minister Jens Stoltenberg's office is in the building, but he is safe. A witness standing at a bus stop near the building saw the blast and watched as it shattered nearly all of the windows in the 20-floor highrise. Nearby offices, including NTB, Norway's leading newspaper and news agency, have been evacuated. The source of the blast has yet to be determined.