GRESHAM, Ore. - Firefighters discovered about 50 marijuana plants in a Gresham home engulfed in flames Saturday night.

It happened at a duplex on Northeast Kane Drive and Northeast Seventh Court about 9:30 p.m.

A neighbor posted a video of the fire on YouTube.

Someone called 911 reporting an explosion and fire at the home. Once firefighters got inside the house and extinguished the flames, they found the pot plants in two different bedrooms, fire officials said.

Police are investigating whether this was an illegal marijuana growing operation.

The man growing the plants had a medical marijuana card. But authorities found far more marijuana plants in the home than the six-plant maximum for medical marijuana patients. If someone grows more plants than the legal limit, they can face criminal charges.

Investigators believe the fire started in the living room, but they were still trying to pinpoint the cause.

Neighbors said they noticed something that smelled like burning plastic in the air about eight hours before the flames enveloped the home.