Engine (with 6) and Tanker 33 responded to a lunch time tractor trailer fire on I81 South. Crews from 33 and Union Fire Co were sent in the area of MM50. Subsequent calls placed the incident north of Exit 52 but southbound. While passing the incident, no conditions were noticed and the response was reduced to 33. After making the flip at MM54.6, the Engine and Tanker arrived at MM52.7. The crew doubled checked the was no fire and released the incident to the trucking firm. Crews cleared within 10 minutes.