MADISON, Wis. -- A fire damaged a restaurant on Madison's East Side Monday night.

The fire at Dimitri's Gyros on East Washington Avenue started just after 10 p.m.

No one was in the building at the time of the fire, WISC-TV reported.

Madison firefighters found heavy flames in the kitchen and knocked down the fire in about 10 minutes.

Fire Department investigators have determined that spontaneous combustion of cotton towels caused the fire.

Investigators learned that towels containing grease and oil from cleaning the restaurant were taken to a laundromat, washed, and dried, then placed in a bag.

Spontaneous combustion refers to a chemical reaction that likely occurred when the oily residue on the still warm towels were confined to the laundry bag and returned to a storage closet near the kitchen around 9 p.m., according to the Madison Fire Department.

The fire was discovered by a passerby about an hour later.

When fire crews arrived, they found smoke coming from the eaves and ventilation system surrounding the building.

The restaurant was closed for the night and there was no one in the building at the time of the fire.

Fire officials estimated that the fire caused $150,000 in damage.