"The car lot could be gone," said Stephen Barnhart, assistant chief of the Hancock Fire Department. "We'll just let it burn off, but it can very well explode because the vent is clogged."
Barnhart said they were trying to keep the building and the tank cool so it would not explode.
Rescue officials received the call about 8 p.m. by a resident by the plant entrance who said he heard an explosion and saw what he thought was smoke.
In addition to the evacuations, I-70 was closed to traffic for two miles east and west at 9:30 p.m. and was expected to remain closed until the burn-off was complete.
West-bound traffic was detoured east toward Williamsport and those traveling eastbound were sent back toward Berkeley Springs, W. Va., and Pennsylvania.
The Rayloc plant produces car alternators, starters and brake parts, said Charles McCurdy, a nearby neighbor who worked at the plant for about 10 years.
McCurdy said the propane was used in ovens to bake on brake linings.
About 350 people work at the plant, McCurdy said.
Fire companies at the scene included units from Hancock, Clear Spring, Williamsport and the Hazard Materials unit and air unit from Washington County.
Other units came from Allegany County, Md., Berkeley Springs, W. Va., South Morgan County, W. Va., and Needmore, Pa.
Fire officials set up a roadblock at the entrance to the plant at Toll Gate Ridge and Rayloc Drive.
A few employees viewed the scene from the top of a nearby hill. However, all they could see were the fire engines coming and going.
Barnhart said officials did not know what caused the fire. The plant was closed for the weekend.
"And it was burning too hot to get close enough to it," he said.