WESTFORD (CBS) — A drug bust this week has first responders concerned about a growing trend. They’re seeing more and more hash oil labs with explosive materials turning up in local homes.

“Butane is a flammable gas that’s heavier than air, so it will sink to low points, and it can be ignited through a variety of ways,” said Fire Marshal Peter Ostroskey. “It’s my understanding that in some cases this is a legal substance, but the activity of creating it is very hazardous.”

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Wednesday, federal drug agents raided a sprawling Westford home, and arrested the family that owns it. Real estate agents Diana and Brad Heath are facing charges along with their daughter, son, his girlfriend, and another friend. Prosecutors say 22-year-old Brad Heath, Jr. was running a hash oil kitchen in the basement, extracting THC from marijuana to create a more potent substance.

Ostroskey says neighbors are lucky it didn’t end the way some others in New England have. In Rhode Island, one man died after a blast in South Kingston a couple months ago. In South Hadley last fall, a refrigerator exploded when hash oil inside gave off butane gas and ignited. In Tewksbury two years ago, a home was destroyed, three injured in a hash oil blast.

“It is a concern,” said Dr. Jeremy Goverman, who has treated people injured in hash oil fires. “We don’t want to see 40 or so explosions before we start legislation to limit the production of these THC concentrates.”

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Colorado has seen hash oil lab explosions jump 167 percent since recreational marijuana became legal.

Ostroskey says first responders in Massachusetts are focusing more training on the hash oil lab scenario, combing forces of the DEA, with the state police bomb squad, and hazmat teams. It’s training they used in Westford this week, as they removed a large oven and butane tank from the property.

“These can be very violent reactions,” said Ostroskey. “It’s a great concern.”

WBZ NewsRadio 1030’s Bernice Corpuz reports

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