Flames burned a large room inside the two-story Long Life Hall.
“There’s a lot of significant damage, but it’s not gutted and the building’s not destroyed,” said Ukiah Valley Fire Capt. Jeff Adair.
Investigators Tuesday were trying to determine the cause of the fire, including whether it resulted from burning incense.
Worshipers gathering for a morning ceremony discovered the fire and called for help just before 3:30 a.m., Adair said. They were unable to put it out with several fire extinguishers.
When firefighters entered the building, flames had burned a worship area at one end of the room, including several foot-tall Buddhas made of powdered marble.
“It had been burning for a long time, hours, smoldering probably,” he said.
There was heat damage throughout the room, estimated to be about 5,000 square feet. At the opposite end stood an altar area, which had been covered in plexi-glass. It was damaged when the plexi-glass melted.
A firewall between the prayer room and a far larger hall helped keep the fire from spreading, he said.
Ukiah Valley firefighters and state forestry Cal Fire firefighters initially responded to the fire, south of Ukiah. A second alarm was issued for more help because of the potential for the fire to spread, Adair said.
As firefighters from Ukiah, Redwood Valley-Calpella and Hopland arrived, the initial crews had the fire under control.
There were no injuries.
The complex originally was the site of the Mendocino State Asylum for the Insane, which opened in Talmage in 1893. It closed in 1972.
The Buddhists bought the property in 1976, including almost 500 acres and more than 70 buildings. The hall that partially burned formerly was a gymnasium.