SAN DIEGO — A fire that erupted inside a Denny’s restaurant in Pacific Beach Thursday morning was ruled arson.

“The fire was started using an incendiary on combustible materials at the restaurant,” said San Diego Fire-Rescue Department spokeswoman Monica Munoz.

Two employees and one customer were inside the restaurant on Garnet Avenue when the fire started at 12:40 a.m., according to fire officials.

Firefighters arrived and found heavy smoke in the restaurant as well as fire in the roof and attic area above the kitchen, Munoz said. Crews were able to knock down the flames around 35 minutes after arrival.

No injuries were reported.

As of 8:40 p.m. Thursday, no arrests had been made and the Metro Arson Strike Team, a partnership between SDFD and the San Diego Police Department, was “still working the case,” Munoz said.

The blaze caused an estimated $700,000 in damage to the structure and $150,000 in damage to the building’s contents, Munoz said.

Metro Arson Strike Team investigators from the fire department attempt to determine the cause of the blaze and police detectives handle the investigation after the cause is determined to be arson.

It was unknown when the restaurant would reopen.