United Fire Company along with Independent Hose Company units were alerted for a reported truck fire on Interstate 70 east bound at the Route 15/Route 340 split. Enroute to the call, Emergency Communications Center advised that they had reports of it possibly being a fuel tanker truck involved in the incident. Chief 3-1 in the area confirming Interstate 70 east bound however at the 51 mile marker with a dry bulk tractor trailer's rear end on fire. Chief 3-1 proceeding to the cross over at Route 40-A. Chief 3-1 advising incoming units to wait until traffic was securely stopped and to proceed west bound in the east bound lanes via the crossover west of the 51 mile marker. Engine 31 arrived on the scene and deployed a 200 foot 1 3/4 inch attack line to begin attacking the fire. Maryland State Police advising that the tractor was in the process of being disconnected from the trailer and there was a fear of the trailer rolling off of the roadway beyond the slow shoulder. As the crew from Engine 31 began their attack of the fire, the trailer succumbed to the soft grass and burned out tires and did eventually roll off of the shoulder into the grassy area, resting on a nearby tree. Crews from Engine Tanker 34 and Engine 12 deployed an additional 200 foot 1 3/4 inch attack line as a back up. Engine 12 also deployed an additional 200 foot 1 3/4 inch attack line for safety reasons. Tanker 1 was on the scene for additional water as needed. Crews brought the fire under control within minutes and determined that there was no extension into the grass or tree. No further hazards existed upon extinguishment. Chief 3-1 releasing the scene to the Maryland State Police and the State Highway Administration. Units clearing the scene as ready.