HAYWARD -- A small house fire late Thursday night led to the discovery of a large indoor marijuana operation, police said.

So far, the owners of the house in the 23500 block of Stonewall Avenue have not been located, said Hayward police Sgt. Mark Ormsby. No one was in the home when firefighters arrived.

Ormsby said police estimate there were about 900 "immature" marijuana plants inside. He said their heights ranged from about 4 inches to 1 foot and none appeared to be ready for harvest. The exact worth of the plants had not been determined. The plants weren't damaged in the blaze.

The fire broke out about 11:54 p.m. Thursday on some electrical lines attached to a wall of the house.

Authorities said the occupants of the house had an illegal power hookup mainly for the grow operation.

Hayward Fire Capt. Don Nichelson said firefighters had to use a chain-saw to cut a hole in the garage door to enter the house and check for occupants and additionalflames. No injuries were reported.

Because of the bypassed power hookup, Hayward police had been called and they were the ones who found the marijuana in several rooms, officials said.

Staff writer Karina Ioffee contributed to this story.