An explosion rocked a Bushwick office Wednesday morning, but only three employees were working, and none were hurt.

Employees at Galaxy Motors say they heard a loud boom and thought something had fallen -- then they entered the room and saw cracked concrete, broken desks and office supplies strewn about.

An official cause for the blast was not immediately available from investigators. Some had speculated that a gas leak could have caused the blast, but National Grid says the company was not called to the scene.

None of the employees were in the room where the blast happened.