SUMMIT COUNTY, Colo. -- A couple at a medical marijuana growing operation were severely burned when the house exploded near Breckenridge early Sunday.

A resident in the house was reportedly using butane gas to make hashish from marijuana when the house blew up about 2:30 a.m. Sunday, the Summit County Sheriff's Office said Monday. Hashish, or hash, is a highly concentrated form of cannabis extracted from a marijuana plant's resin-rich flower clusters.

Emergency responders found "bloody footprints in the snow" along with the shattered remnants of blown out windows, insulation and other debris scattered around the house, sheriff's spokesman Tracy LeClair said in a statement.

A local fire marshal warned that using butane to extract the active ingredient THC from marijuana should never have been attempted inside the home. Four empty cases of butane fuel canisters were found in the home.

“When butane is used indoors, severe injury or death may result,” explained Fire Marshal Jay Nelson of the Red White and Blue Fire Department.

An uninjured male roommate drove the burned man and woman to Summit Medical Center, and they were later transferred to University of Colorado Hospital in Aurora.

The burn victims were not identified, because of medical privacy laws, LeClair said. The pot growing operation was deemed a legal dispensary under Colorado Amendment 20, because several medical marijuana registry cards were discovered in the home, LeClair said. Numerous marijuana plants of varying sizes were also inside.

The male roommate told deputies said he believed the explosion occurred when one of his roommates attempted to make hash in their room through a TCH-extraction process using butane gas, according to the sheriff's office statement. The man said his roommate had made hash several times in the past, usually in the garage.