A criminal investigation has been opened after rescue crews discovered an illegal fireworks manufacturing facility inside the charred remains of a building in Nevada County.

When CalFire crews arrived at the scene of a fire along Old Stagecoach Road in the Chicago Park area of Nevada County, the found a 57-year-old man with severe burns to his face and upper torso.

As they began fighting the fire, crews also found large amounts of materials used for making fireworks, according to CalFire.

Law enforcement as well as explosives ordinance crews were called to the scene, and the criminal investigation began.

Due to the volatility of the chemicals found at the home, along with the additional materials for making the illegal fireworks, the decision was made to destroy the items in place, Nevada County sheriff’s deputies said. Only a handful of live ordnances were found and destroyed; however, there were large amounts of precursor chemicals and hardware found for making fireworks.

Based on the evidence found at the scene, investigators believe the injured man was handling a live ordnance inside the bottom floor of his two-story home when the device exploded, resulting in his injuries.

Due to the severity of his burns, the victim was transported by air ambulance to the UC Davis Medical Center in Sacramento, where he is expected to survive.