Police were investigating a marijuana grow that was discovered Wednesday by firefighters battling a two-alarm blaze that badly damaged a home in North San Jose, authorities said.

The San Jose Fire Department responded to a residential fire at a two-story house in the 1800 block of Fumia Place near Oakland Road around 3:10 p.m.

When crews entered the home, they immediately saw a pot-growing operation, fire Capt. Reggie Williams said.

The interior of the home had been equipped with special lights and a ventilation system to facilitate the growth of the plants, Williams said.

The fire appears to have started on the second floor, where most of the plants were kept, but then spread to the first floor, Williams said.

At one point, a second-floor bedroom collapsed to the first floor, but no firefighters were injured.

They knocked down the blaze at 3:49 p.m. and declared it under control at 4:31 p.m.

Firefighters encountered dangerous electrical wiring, and had to contact PG&E to shut off power, Williams said.

No one was home at the time of the fire, which caused major damage to the 2,300-square foot, single-family house.

Firefighters notified police at about the pot grow at 3:16 p.m., and officers seized about 80 partially grown pot plants, police said.

Someone had installed an illegal electrical system that bypassed an electrical panel, police said.

Police are still looking for suspects in the case.