Firefighters were battling a blaze at a 9,111-square-foot home in Mount Washington Thursday night, the Los Angeles Fire Department said.

The fire broke out at a home in the 4000 block of North Sea View Avenue around 8:35 p.m., according to fire personnel. At 11:10 p.m. LAFD said it would monitor the scene overnight extinguishing hot spots and stabilizing the structure, and full extinguishment of “stubborn flames” would be declared later.

Late Thursday night firefighters were still searching for the home’s owner, an 84-year-old man, who was the only person unaccounted for out of the home’s 12 residents, LAFD said.

One woman, 74, had been rescued from the home and was in fair condition but suffering from smoke inhalation, according to officials, while others were able to escape unharmed.

A man who said he lives at the home told KTLA he had heard what sounded like a large explosion when the fire broke out, and when he went to warn the owner to escape, the 84-year-old instead ran into his bedroom.

A large crew of143 firefighters had been dispatched to the scene and three helicopters were dropping water on the flames.

The fire, which began in on the second subterranean level of the descending hillside home, spread to all its three levels within an hour, authorities said.