The Rocklin Police Department reports a small honey oil operation caused the explosion at a 2nd Street apartment complex.
"All the sudden I felt the floor roll, and my ears pop, and I heard glass shattering," said neighbor John Roberston.
Robertson said he lives upstairs from the apartment where the explosion happened.
As of 8:30 p.m., it was unclear if the building would be safe to re-enter. A structural engineer will assess the damage to the building Monday and determine what repairs need to be made before residents are allowed to return home.
"Threw open their window, shoved the hose through the window and said, 'Put the freakin' fire out.' They looked at me like I'm dumb. 'What do we do with the hose?'" Robertson recalled. "There was a fire in the bathroom, basically what was going on."
A suspect ran from the scene of the explosion and has not been found by Rocklin police.
"My understanding is, we only had one person who had some real minor injuries," said Sgt. Gilbert Farrulla. "Nobody was transported to the hospital."
Other residents of the apartment building could be seen carrying belongings to their cars as they looked for somewhere else to stay.
Robertson said he's been suspicious about drug activity in the apartment beneath his for some time.
"Oh, I'm mad as heck. Yeah, I go to work everyday, I do it the right way. And you got people who sit at home and do this kind of dumb s*** all day," he said.
Stay with FOX40 News for more updates on this developing investigation.