SAN JOSE, Calif. -- Firefighters are working to extinguish a two-alarm fire that started Saturday afternoon on the second floor of a home in San Jose, a fire spokesman said.

The fire was reported at about 1 p.m. in the 1500 block of Darlene Avenue, according to fire Capt. Scott Kouns. The homeowner was inside, but was not aware of the fire, he said.

A neighbor knocked on the door and notified the home's occupants that the roof was on fire, Kouns said.

Firefighters arrived to find flames coming out of the roof, he said. Crews contained the fire before it could spread beyond the home's attic and second floor.

Nobody was injured in the fire, Kouns said.

Crews were still on the scene as of 3 p.m., dealing with small pockets of remaining flames, Kouns said.

About 30 firefighters responded to the blaze. Fire investigators do not yet know what caused the fire.