It happened at a house in Dinuba on Marion near Milsap.
Dinuba fire firefighters say the men were using six to eight cans of butane inside a small enclosed laundry room to make the drug.
The fumes built up and then, the pilot light of the water heater sparked a flash explosion. The explosion's force blew off a door and pushed a wall off of its foundation by six inches.
Investigators say kids and other family members were in another room of the home at the time of the explosion.
They say the family is lucky the damage wasn't worse. "Very scary, the kids were just in the other room, just adjacent to the room where the individuals were working in," Chief Chad Thompson said.
One of the men had second degree burns on his legs, arms, face and hands. Both are expected to be okay but could face criminal charges.