SYLMAR (CBSLA) — A marijuana dispensary is now at the center of two investigations into a fire that raged through a Sylmar strip mall and threatened a home behind it early Monday morning.

The blaze was first reported just before 4 a.m. at 12777 N. San Fernando Rd., according to Los Angeles Fire Department dispatcher Margaret Stewart said. It took more than 100 firefighters three hours to put out the stubborn fire.

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Firefighters were able to save all but three of the businesses in the strip mall — a convenience store, the marijuana dispensary and a Mexican restaurant that opened just a month ago.

The blaze was particularly difficult to get a handle on because the businesses in the L-shaped strip mall all shared attic space and an outer facade that collapsed.

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“We did have evidence of smoke only when we got here, then we got fire, then we had collapse,” a battalion chief said of how quickly the fire escalated.

No injuries have been reported.

San Fernando Boulevard was shut down for most of the morning. Firefighters were also sent to protect a home located close behind the strip mall.

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The strip mall blaze sparked two investigations — one from arson investigators who will determine where and how the fire originated, and a LAPD investigation that is focused on whether the marijuana dispensary, which had been in business for five years, was licensed and complying with local laws.