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LONGMONT, Colo. — Two people suffered burns in an explosion in Longmont on Wednesday after trying to extract oil from marijuana. Police say it’s just the latest example of a dangerous trend.

Longmont police say three people will face arson charges after the small explosion inside a garage. Though there wasn’t extensive damage to property, witnesses reported a briefly chaotic scene.

“They heard an explosion,” said detective Jeff Satur with the Longmont Police Department. “The garage door came open, they observed several people run out of the house that were on fire.”

“I was definitely concerned. I sprinted over to their house,” said Dan Krauss, who lives across the street.

Krauss said he was relieved to see police and firefighters arrive quickly, getting one man, with serious burns, the help he needed. But Satur says the three victims are now also suspects in an arson case.

“We believe they were doing a butane extraction, trying to capture hash oil,” Satur said.

Hash oil, also known as hemp oil or honey oil, is a potent, liquid form of marijuana often extracted using butane. That process can also generate potentially explosive vapors.

“All it takes is one quick spark,” said Jerry Means, an arson investigator with the Colorado Bureau of Investigation. “The pilot light on a water heater or a furnace and kaboom.”

Similar blasts, have happened across the state in recent months. According to a recent bulletin by the Colorado Information Analysis Center, a blast in Lakewood caused injuries in February.

An explosion in Carr in August not only blew out windows but moved the outside walls of a home. Colorado Springs police have investigated two incidents in just the past few months including one last week at an apartment complex.

“We’ve had situations where there are small children in one side of the house and then they’re manufacturing this hemp oil in the other side of the house,” Means said.

People who live near the home where the latest explosion took place said they relieved it wasn’t worse.

“I took a great deal of comfort in knowing it was not a meth lab,” Krauss said.

Police looked at it differently.

“They put the neighborhood at risk,” Satur said.