The cause of the blast, in a vacant apartment unit in the rear of the structure, appears to be linked to a marijuana grow inside, said Det. Renee Witt with Seattle police.
Investigators from the Seattle Police Department's Arson Bomb Squad determined the explosion was caused by butane tanks being stored in the freezer. Because it is heavier than air, the butane gas leaked to the bottom of the refrigerator. When the appliance started up, an electrical spark ignited the butane gas causing an explosion.
Witt said butane is used to extract the THC from plants. It's not known yet whether it was a legal grow operation or not.
Fire crews responded to the scene, in the 2800 block of South McClellan Street, at about 1 p.m. after receiving a report of an explosion, a Seattle Fire Department spokesperson said.
Firefighters arrived and evacuated the flower shop located in the front of the building.
A Puget Sound Energy crew shut off the gas to the building and Seattle City Light shut off power. A structural engineer from the Department of Planning and Development is heading to the scene to assess the structural integrity of the building.
There were no injuries and the building will remain evacuated until the structure is deemed safe to reoccupy.