It is still a mystery how a truck caught on fire while driving in the Town of Union on Thursday. The Brusels-Union-Gardner Fire Department, Door County Sheriff’s Department, and Door County Emergency Services responded to the blaze that occurred off of State Highway 57 near County D just after 8:45 p.m. where a truck was pulled off to the side of the road fully engulfed. Firefighter Matt Phillips said the driver of the vehicle pulled over when he noticed smoke coming from the vehicle but did not know how it would have caught fire. Four firetrucks spent about an hour on the scene, two of which were used for traffic control since the incident occurred on the decline of a hill.  No one was injured in the fire, but the cause remains unknown.