Five firefighters were hospitalized Saturday morning after noticing an unusual burning sensation on their faces while responding to a blaze at an unpermitted cannabis operation in downtown L.A.

Brian Humphrey, a Los Angeles Fire Department spokesperson, said there was concern that the sensation may have resulted from burning chemicals inside the two-story, brick building south of the Arts District.

“These were seasoned firefighters,” he said, “who felt something out of the ordinary.”

None of the five cited other complaints, Humphrey said, nor were they having trouble breathing.

By Saturday evening, Humphrey said, all of the firefighters had been released from the hospital and returned to duty.

The callers who reported the blaze along an industrial strip said it seemed that one or more people may have been inside the burning building, Humphrey said.

Two cadaver dogs went to the scene, but there was no evidence that anyone was inside.

A Los Angeles Fire Department spokesperson said there was concern that the firefighters had a reaction to burning chemicals inside the building south of the Arts District.

(Andrew Gombert / Los Angeles Times)

The cause of the fire remains under investigation, Humphrey said, adding that it isn’t clear whether cannabis was being grown in the building or being processed inside.

Last month, a body was recovered from an explosive fire at what police described as a “clandestine” cannabis lab in South L.A. In 2022, at least four people, including two firefighters, were injured in an explosion at a makeshift lab in Orange County used to process hash oil, which is extracted from marijuana plants using butane.

Times staff writer Hailey Branson-Potts contributed to this report.