Watertown Fire Rescue was called out at approx. 10:15pm for a trailer house fire at 929 40th St SW. Upon arrival firefighters found flames coming out the front of the trailer house. There were no occupants home at the time but a family pet was lost in the fire. The trailer house is considered a total loss. Firefighters remained on scene for approx. 3 hours. There were no other reported injuries. The cause of the fire is still under investigation.