Arson units are investigating the cause of a duplex fire in northeast Houston.

According to the Houston Fire Department, firefighters arrived at the house located on Crane and Pickfair Street around 3 a.m. Tuesday.

Upon arrival, fire crews discovered heavy smoke coming from the left section of the duplex. 

Firefighters made a fast attack and were able to knock the flames out in about 20 minutes.

Both sides of the duplex are occupied, but no one was home at the time of the fire.

The flames left heavy fire damage to the left unit and smoke damage to the unit on the right.

The cause of the fire is still under investigation.