LOS ANGELES (CBSLA) — Officials continued the investigation Monday into the cause of an explosion at a downtown Los Angeles smoke shop Saturday that sent a dozen firefighters to the hospital.

Investigators said they believe the explosion at Smoke Tokes was likely caused by butane hash oil, though it was not immediately clear whether the business was producing the oil — which is illegal in the city — or selling it.

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A video posted in 2018 to YouTube channel The Pot Network appears to show an interview with the owner of Smoke Tokes talking about the business that sells vaping and smoking paraphernalia.

“Anything a smoke shop wants, we pretty much carry,” the owner said.

But according to the Los Angeles Department of Cannabis Regulation, there were no commercial license records associated with the location in the 300 block of East Boyd Street, and the Los Angeles Fire Department said it had no records of inspections, though the department said it was familiar with the business.

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A similar fire broke out in 2016 just one block away from Saturday’s blaze at a previous Smoke Tokes location. The cause of that fire was never determined.

And a February letter from the Food and Drug Administration warned the business that required nicotine warning labels on its products were misbranded.

The owner of Smoke Tokes could not be reached for comment.

Four of the firefighters injured in the blast remained in the hospital Monday. They were all said to be in stable condition.

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LAFD fire investigators are cooperating with the Los Angeles Police Department and the Bureau of Alcohol, Tobacco, Firearms and Explosives in the ongoing investigation.