Spontaneous combustion is the cause of an early morning fire behind Pop's Pizza in Quincy.
Quincy firefighters responded to the back area of the restaurant on Maine Street around 3:30 Monday morning. When they arrived, they found heavy smoke and flames coming from above the garage portion of the building in the rear of the restaurant.
Firefighters quickly put out the fire and then worked to extinguish hot spots to keep it from spreading through the walls to other parts of the building.
Investigators were called in. This is standard proceedure if a cause isn't determined right away.
Quincy Fire Chief Joe Henning says the rags that caught fire were stored in a hamper.
There is reportedly smoke and water damage in the restaurant.
KHQA was on the scene and will have more details as they become available.