Crews from Morecambe and Lancaster raced to Southgate on White Lund on Sunday at 1.39pm and found a Trust Medical ambulance that was being routinely cleaned, well alight.
Crew manager Jim Davison said: “We were fairly concerned because there were reports there had been explosion and the ambulance was only three metres from a nearby building.
“It went up very quickly because there is a lot of plastic and the guys on the scene thought they had put the fire out with a foam extinguisher, but it reignited and had to be extinguished.
“The ambulance was severely damaged by the fire.
“The employees did exactly what they needed to do, get back, get away and call the fire service.
“Another five minutes and the fire could have caused major problems.
“They called us as soon as possible which makes all the difference.”
There were no injuries and the fire was accidental.