The blaze in the North Hollywood house was reported early Monday and firefighters extinguished it in about 30 minutes.
But authorities say firefighters also discovered about 70 marijuana plants being grown hydroponically in two rooms outfitted with lighting systems.
Fire Battalion Chief Peter Benesch tells KTLA-TV the extra electrical equipment may have overheated the power system and sparked the fire.
Police Sgt. Aaron Ponce says one person has been arrested.
There were no injuries.