Cooking oil left unattended on a stove top is suspected to be the cause of a Friday afternoon blaze at a senior apartment complex on Petaluma’s east side, fire officials said.

Petaluma firefighters responded to the Vintage Chateau Senior Apartments on the 300 block of North McDowell Blvd. about 12:15 p.m. after receiving reports of a structure fire. They arrived to find a second-floor unit filled with smoke that was also drifting into the hallway, Battalion Chief Jeff Schach said in a news release.

The blaze had already been doused by sprinklers that activated inside the unit, he said.

An elderly couple and their daughter who had been inside at the time of the fire were evaluated for smoke inhalation, but were not transported to the hospital.

Other senior residents were also evacuated from the smoke-filled hallway, Schach said. No injuries were reported.

Water from the sprinklers prompted “significant flooding” in the kitchen and caused minor damage to the ceiling of the apartment below, Schach said. The blaze, which is believed to have started after the cooking oil caught fire, also caused moderate smoke damage to the wall and cabinets.

Firefighters helped to clean up and remove water from the apartments, and Red Cross was notified. The residents in the unit where the fire started will find other accommodations for the night, though the downstairs neighbors were not displaced, he said.

Damage was estimated to be about $5,000.

Personnel from Cal Fire and Rancho Adobe Fire Protection District also responded.