On September 29, 2013, the Santa Cruz Fire and Police Departments responded to an explosion and fire at an apartment building in the 700 block of Third Street. As they arrived, officers and fire personnel were confronted with additional explosions from butane canisters. These explosions hindered fire suppression and rescue efforts by emergency personnel. 
In spite of the additional explosions, Firefighters were able to contain the blaze and minimize damage to the surrounding structures, and Police Officers were able to evacuate nearby residences.
Three individuals suffering life threatening burns were able to flee the building. All three received immediate medical attention at the scene. They are currently in extremely critical condition at a Bay Area trauma center.
The investigation revealed that the three individuals were involved in hash oil production at the time of the blast. This process uses chemical solvents like butane to extract the hash oil from marijuana. Butane fumes are heavy and typically travel low to the ground. The primary blast area in this explosion indicates the pilot light from a water heater. The wall next to the water heater was blown out in the explosion, with the fire flashing back into the small storage room where the victims were located.
In February 2013, FEMA issued an alert to Police and Fire departments warning of an increase seen in hash oil production explosions. The alert is found here
http://www.usfa.fema.gov/fireservice/emr-isac/infograms/ig2013/6-13.shtm#1
The end product is commonly referred to as “BHO” (Butane Hash Oil), and “Honey Oil”.
The victims are males, ages 23, 25 and 23. All three are Santa Cruz residents. Two of the three reside at the apartment complex.
Investigators are continuing to follow up with the fire and pending criminal investigation.