A suspected pipe bomb exploded at a federal courthouse in downtown San Diego, damaging the front entrance and blowing out a window, authorities said. No injuries were reported.
Few people were around the building, which is a block from nightclubs in the Gaslamp Quarter, when the powerful blast also damaged the lobby area of the Edward J. Schwartz Federal Courthouse about 1:40 a.m. Sunday, said FBI spokeswoman April Langwell.
The bomb was reported by two guards in the building, who were uninjured. About 40 agents combed the front courtyard after the area was swept for explosives. No arrests have been made.
Debris was found lodged in a window about eight stories up the AT&T building that faces the courthouse.
The evidence collected will be sent to an FBI laboratory in Virginia for analysis by bomb experts.
Authorities said that surveillance cameras outside the building may provide information, but that no cameras directly face the doorway.
Streets in the area were closed until early Sunday afternoon. The courthouse will remain closed Monday as repairs are made.
No one has claimed responsibility for the blast, authorities said, and no threats were received before the bomb was left.