Fire investigators are looking into what caused a fire that forced the evacuation of the Arroyo Grande Walmart yesterday. Just before noon, Firefighters from the Five Cities Fire Authority, and San Luis Obispo City Fire Department responded to a commercial fire. When they arrived, crews found smoke billowing from a storage area at the back of the store. It took firefighters about 20 minutes to knock down the flames. The fire did not make it into the store. No one was injured.