OCEANSIDE, Calif. -- A pre-dawn fire Thursday was apparently sparked by an overload of electricity that may have been tapped illegally to power lighting for a suspected marijuana-growing operation, authorities said.

Firefighters responding to the blaze at 94 Avenida Descanso at 12:55 a.m. entered the home's garage and found a "very elaborate and well insulated indoor greenhouse and what appeared to be several hundred marijuana plants being cultivated under artificial lights," said Oceanside fire Battalion Chief Pete Lawrence.

Heavy smoke filled the garage, he said, adding that that flames shot from a wall near an electrical panel and traveled up the wall and into the home's attic.

The flames were knocked down within 15 minutes, but due to additions in the garage and thick insulation around the alleged plant-growing area, crews remained on scene until 2:30 a.m. extinguishing pockets of fire, he said.

Paramedics treated a resident at the scene for smoke inhalation. The man was later airlifted to UCSD Medical Center for treatment, Lawrence said.

A fire investigator determined the blaze originated in an area of the wall where the home's occupants illegally tapped into power lines feeding the residence, Lawrence said.

The fire caused about $45,000 damage to the home's structure and contents, Lawrence said, adding that none of the suspected marijuana plants were burned.

The Oceanside Police Department is investigating.