Pomona Police & Los Angeles County Fire are investigating a arson fire that was reported around 8:30pm Thursday night located in the 500 block of W. Holt Ave. Firefighters arriving on scene encountered flames raging through the windows on the second floor of the apartment units, located above a commercial building. Firefighters quickly went into offensive mode and were able to knock down the fire within 30 minutes. No injuries have been reported. Officers located a witness at the scene that is assisting with the investigation. Arson Investigators are en route to the scene.