The bodies were found on private property on July 1, sheriff's Capt. Tracey Stuart said. The marijuana was growing without the property owner's knowledge or consent, Stuart said.
Napa Special Investigations Bureau agents familiar with the area found the bodies in the growing operation that contained 3,000 immature plants that were about 2 feet tall, Stuart said.
The identities of the victims have not been confirmed but they are not related to the property owners, Stuart said.
The narcotics agents eradicated the marijuana operation, believed to be part of a larger Mexican drug trade operation, on July 6, Stuart said. The gardens were concealed by the natural vegetation on the hillside, Stuart said.
The sheriff's office is interviewing "tons of people" who are involved in marijuana growing in Napa County, Stuart said.
"They are definitely getting more violent and armed," Stuart said of the growers.
Marijuana growing operations are typically found near Lake Berryessa and in rural areas on the east and west sides of Napa Valley, Stuart said.