SEATTLE Wa (CNN) -- An attempt to make hashish out of marijuana ended in an explosion Tuesday at a private residence in Seattle, authorities said.
The impact of the blast blew one wall of the building six inches off its foundation, said Seattle Fire Department spokesman Kyle Moore. It did not cause a fire.
The explosion ripped off a glass sliding door and smashed windows, CNN affiliate KING said. No injuries were reported.
A woman was working in a flower shop housed in the same building at the time, Moore said. She got out and alerted authorities.
Police arson and bomb experts believe that butane used to extract the hash oil caused the explosion, Seattle Police said.
The gas, which is heavier than air, seeped from a bottle in the freezer compartment down into the bottom of the refrigerator, where the electrical wiring ignited it, Moore said.
Police officers and firefighters found marijuana in the freezer and one bedroom, as well as a growing operation in the basement, authorities said. They notified narcotics detectives.
Arson and bomb police will follow up on charges of reckless endangerment.
As in the state of Colorado, voters in Washington State approved the regulated sale of cannabis at approved shops last year.
Colorado's law took hold with the new year, but Washington won't open marijuana retail outlets until later in 2014.