New York City Mayor Michael Bloomberg says officials don't have "any idea" who was behind two blasts that hit the Manhattan building housing the British Consulate early Thursday morning.
The blasts didn't injure anyone and only caused slight damage to the building.
Police say the explosive devices were "novelty grenades" that had been filled with gunpowder and may have been lit by a fuse.
Police Commissioner Raymond Kelly says officials don't know the motive for the attack. And the mayor says there was no warning ahead of time.
Bloomberg says the culprits used "a relatively unsophisticated explosive device."
He also says officials are reviewing building surveillance cameras and are asking people who see anything suspicious to call them.
Officials say they inspected other foreign diplomatic sites in the city and found nothing.