The blast occurred at a facility where systems are produced to reduce noise resulting from the testing of large-caliber cannons.
One worker received burns on 80 percent of his body, police said. Another broke his leg trying to escape the explosion.
The ages of the injured were not released, but ranged from 48 to 68.
The employees were trying to dismantle scrap metal and a steel pipe with a torch when the flame unexpectedly struck a flammable substance, possibly wood-grain alcohol residue, according to police.
"It ignited and exploded. A plume of smoke probably went up 30 feet from the structure," said the officer.
About a dozen people work at the Wright-Malta work site.
Town officials activated the communications portion of the town's emergency response plan when they heard initial reports of the explosion. They were worried that they might have to order an evacuation of the nearby Luther Forest subdivisions, where about one-third of the town's 13,000 residents live.