Eleven US firefighters have been injured in an explosion at a hash oil manufacturer in Los Angeles.

The fire crews had gone inside the complex in the city’s Toy District after an initial report of a fire, but then had to run for their lives when a ball of flames exploded out of the building and scorched a fire engine across the street.

Los Angeles Fire Department captain Erik Scott said “one significant explosion” occurred about 6.30pm local time on Saturday.

Firefighters inside had to run through a wall of flames he estimated to be 10 metres high and wide, and those on the roof scrambled down a ladder that was engulfed in fire.

I am profoundly grateful for & proud of the men & women of the @LAFD who responded to the Major Emergency fire Downtown this evening and I am hopeful that all 11 members who were injured are on the road to recovery. Thank you all for your support of our firefighters.

— Chief Crowley (@LAFDChief) May 17, 2020

He said people at the scene described the explosion as sounding like a freight train or jet engine.

The fleeing firefighters tore off their protective equipment that had burned and helmets that had melted, Scott said.

“The was one of the worst scenes I’ve seen,” he said.

https://twitter.com/seanmiura/status/1261834618182877184

More than 200 firefighters rushed to the scene, as the flames spread to several nearby buildings.

Scott said the building was a warehouse for SmokeTokes, which he described as a maker of “butane honey oil”.

Butane is an odourless gas that easily ignites, and it is used in the process to extract the high-inducing chemical THC from cannabis plants to create a highly potent concentrate also known as hash oil.

The oil is used in vape pens, edibles, waxes and other products.

On its website, SmokeTokes advertises a wide variety of products including “puff bars”, pipes, “dab” tools, vaporisers, “torches and butane”, and cartridges.

-AAP