The fire was initially reported at 327 East Boyd St. just before 6:30 p.m.
California Gov. Gavin Newsom said on Twitter he was "grateful for the fearless firefighters and first responders on the scene battling these flames tonight". The fire spread to several nearby buildings, but firefighters were able to douse it in about an hour.
The department issued a "mayday" call and characterized the incident as a "major emergency".
At least ten firefighters have reportedly been injured. News helicopters showed dozens of fire trucks at the scene on Saturday (Sunday NZ time).
'We faced a very hard situation and a significant incident.
Crews had entered the building to battle what was initially thought to be a minor blaze when they noticed that the smoke pressure was escalating and made a decision to evacuate, Los Angeles Fire Department chief Ralph Terrazas told reporters. But firefighters started to hear a rumbling, high-pitched sound, and a call was made for everyone to get out. They managed to completely extinguish the blaze by 8:08 p.m.
Four were taken to the burn intensive care unit, while the others were taken to the burn ward, he said.
10 firefighters injured in EXPLOSION responding to multi-building blaze in Los Angeles (VIDEOS)
Mr Scott said the business was a maker of butane honey oil.
It was unclear on the number of casualties, but the LAFD said on Twitter that up to 10 firefighters were "down" after the blast. The cause of the explosion has yet to be confirmed.
Firefighters, who were inside and on the roof of the one-story commercial building had to evacuate and were forced to run through a wall of flames.
Terrazas said firefighters saw butane canisters inside the building and outside on the street but it was unclear what caused the blaze.
A medical team was on the scene treating the firefighters and transporting the injured to hospitals.
The LAFD urged people in the area to find a way to shelter from the smoke.
An LAPD officer keeps watch on a multiple structure fire as LAFD firefighters work following an explosion on May 16, 2020 in Los Angeles, California.
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