Calaveras County Sheriffs deputies discovered several incendiary devices and improvised weapons in the garage of a Summit View home in Arnold.
Deputies called in the Calaveras County Bomb Squad and sheriffs department detectives and evacuated the surrounding homes.
Investigators say the fire bombs were made of combustible liquid in glass jars fitted with wicks. The weapons were lengths of pipe equipped with ammunition.
The discovery is under investigation and sheriff officials expect arrests to be made in the case.