Arson units are investigating what caused a fire to start at a metal shop in east Houston.

It happened around 2 a.m. Wednesday at the National Oilwell Varco shop on Garrow Street.

Fire officials said the fire started inside the shop’s office. No one was at the business at the time the fire started.

Firefighters with the Houston Fire Department had to use a Super Vac to evacuate the smoke out of the building.

Officials said the office suffered extensive fire damage.

Arson investigators were called to the shop to determine what started the fire.