PASADENA, Calif. (KABC) -- An explosion that left one person with severe burn injuries at a Pasadena home Monday was confirmed as a drug lab fire, according to investigators.The explosion happened at a back shed of a home in the 1900 block of E. Washington Boulevard, near Allen Avenue. It was unclear what time the blast occurred.Officials said a man in his 20s suffered severe burns to his arms and face and was hospitalized in unknown condition.Bundles of marijuana, pots and pans and hundreds of butane canisters were being investigated at the scene by the drug task force L.A. IMPACT. Detective Scott Schulze of the task force, which operates under the Department of Justice, said the incident was a honey oil lab explosion. Schulze explained the honey oil operation is the chemical extraction of THC from marijuana."Very dangerous. About a third of the labs we go to of this type have already blown up," Schulze said.The lab was described as a medium-sized operation and among the evidence, law enforcement also located two weapons, including an assault rifle."It's a lucrative business. They're selling the finished product for large amounts of money," Schulze added.Investigators, including the Los Angeles County Fire Department Hazmat Division, were continuing to look into the cause of the explosion.