LOS ANGELES — An explosion Saturday at a hash oil manufacturer in downtown Los Angeles injured 11 firefighters who had gone inside the building after an initial report of a fire.

Los Angeles Fire Department Capt. Erik Scott said “one significant explosion” shook the neighborhood around 6:30 p.m., and as first responders arrived they saw firefighters emerge from the building with burns and other injuries. He did not provide conditions on the injured.

He described the business as a maker of “butane honey oil.” Butane is an odorless gas that easily ignites.

The process of making the oil involves extracting the high-inducing chemical THC from cannabis plants to create a highly potent concentrate also known as hash oil. The oil can be used in vape pens, edibles, waxes and other products.

Firefighters were initially called to 327 East Boyd St. in the city’s Toy District for a report of a fire at a one-story commercial building. Firefighters entered the building, and there was nothing unusual until the explosion occurred.

More than 200 firefighters rushed to the scene and dozens of engines, trucks and rescue vehicles clogged the streets. The fire spread to several nearby buildings, but firefighters were able to douse it in about an hour.