FREDERICK, Colo. (AP) — The extraction of hash oil is likely to blame for an explosion that injured two men in a trailer in northern Colorado.

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The Weld County Sheriff’s Office says a 32-year-old man and a 71-year-old man were being treated for serious burns after Monday night’s blast near Frederick. Investigators ruled out that the explosion was related to the oil and gas industry and say butane was likely being used to extract hash oil from marijuana.

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Teresa Anderson, who owns the nearby B Bold Ranch RV Park and Storage, says she heard “a big boom, one big boom” just after 8 p.m. The trailer was engulfed in flames when deputies arrived.

The men, whose ages were initially listed as 20 and 70, were in serious condition Tuesday.

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