Three men were taken to the hospital with severe burns -- one of them is in critical condition.
Authorities say the process of making honey oil from pot is extremely dangerous and requires the use of butane which is highly flammable.
In this case, investigators say the victims weren't careful enough. "The butane fumes traveled along the floor... and pretty much exploded that room," said Michael Ortiz, Fresno County Sheriff's Office.
Investigators say the number of honey oil makers is on the rise in Fresno County. They say they've already dealt with six similar cases of people being injured because of explosions.
Authorities aren't saying what charges will be filed in this latest case.