Firefighters battling a Boyle Heights blaze early Wednesday morning discovered a marijuana growing operation inside an industrial building.

The fire was reported at 2:40 a.m. at a single-story building on East Olympic Boulevard, according to the Los Angeles Fire Department. Less than an hour later, officials reported the grow.

After a large air conditioning unit fell through the building’s roof, crews also discovered bottles and tanks of unknown chemicals inside the structure. The Fire Department’s hazardous materials squad was on the scene.

It took 93 firefighters to extinguish the blaze. Arson investigators were also called in. No injuries have been reported.

Fire Department spokeswoman Margaret Stewart said it was unclear whether any arrests would be made, as the investigation had not yet determined whether the marijuana grow was illegal.