It happened around 9:45 a.m. at 2557 Geryville Pike in Upper Hanover Township.
Firefighters say a vehicle blew up, burning two workers.
Rescuers say, when they arrived, they found a fire inside a garage at the yard.
One had to be flown from the scene by medical helicopter. Another was taken to the hospital by ambulance.
The fire department was able to get the flames under control in about 20 minutes.
