Watertown Fire Rescue responded to a fire at the Concrete Dakota cement plant at 3:15 on Thursday afternoon. Upon arrival firefighters found a Peterbilt semi-tractor with fire coming from the engine compartment. Crews were able to quickly extinguished the fire before it could spread to anything else. The truck was not running and not close to any buildings. The engine block heater was plugged in and believed to be the cause of the fire. Crews were on scene less than 30 minutes. WFR would like to remind people to be careful when using block heaters in cold weather. Be sure to check them over and make sure the cords are in good condition.