A butane “honey oil” operation was discovered Wednesday morning inside a commercial building in Boyle Heights, where a fire burned for nearly an hour before being extinguished by firefighters.

Crews arrived at 3529 E. Olympic Blvd. at 2:40 a.m. and found flames burning through the roof of the 50-by-50-foot building, the Los Angeles Fire Department reported.

Firefighters made their way inside and encountered heavy smoke with very little visibility, according to Margaret Stewart of the LAFD.

A hazardous materials team was sent to the scene due to the discovery of bottles of unknown chemicals and gases inside the building, she said. A large air conditioning unit had fallen through the roof.

Firefighters initially reported finding a marijuana grow operation in the building and later classified it as a butane “honey oil” operation, Stewart said. Honey oil labs are extremely dangerous because the process involves extracting a concentrated form of THC from marijuana using butane.

A total of 93 firefighters extinguished the flames in 54 minutes, Stewart said. No injuries were reported.

LAFD arson investigators and law enforcement personnel were conducting an investigation.

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