The main gate of the Chinese consulate in San Francisco was set on fire on Wednesday night.
Consular officials said an unidentified person parked a van in front of the mission, then poured two cans of petrol on the main gate and set it ablaze.
The BBC reports no-one was injured, but officials said the building was "severely damaged".
The incident happened at about 9.30pm (local time).
The FBI said it did not know whether the consulate had received any recent threats.