Ventura firefighters responded late Friday night to a report of a residential structure fire on the 300 block of Walnut Drive in Ventura. According to officials with the Ventura Fire Department, investigators determined that an explosion occurred when flammable butane vapors were ignited during an extraction process of THC from marijuana. The first firefighters to arrive reported no sign of fire, reports the Ventura County Star. Upon their initial investigation, it was determined that an explosion had occurred resulting in structural damage to the residence and a small fire had been extinguished by the resident. [...]