Eight illegal cannabis operations in Northern California have been shut down following a two-month investigation led by the Nevada County Sheriff’s Office and the state Department of Fish and Wildlife.

Between September and October, investigators served search warrants at eight locations, the sheriff’s office said, including four in Nevada City, two in North San Juan, one in Grass Valley, and one in Smartsville. All were found to have illegal cannabis grows.

More than 5,000 plants were destroyed across all sites, while investigators said they seized over 1,500 pounds of processed cannabis and recovered one unregistered firearm.

Fish and Wildlife officials arrested one person on Sept. 26. That person was booked into the Wayne Brown Correctional Facility in Nevada City on multiple felony charges, including illegal cannabis cultivation, possession for sale, and environmental violations related to water pollution and wildlife protection.

Another homeowner in Grass Valley was cited and released on Oct. 1 for illegal cultivation, the sheriff’s office said.

After further investigation, the sheriff’s office said detectives also filed additional charges with the Nevada County District Attorney’s Office against five more individuals connected to four of the properties. Those charges include illegal cannabis cultivation and environmental violations similar to the first person who was arrested and charged.

The joint operation focused on grows suspected of polluting waterways, illegal dumping and causing water runoff. Several agencies assisted with the enforcement, including the Eradication and Prevention of Illicit Cannabis (EPIC) Task Force, California National Guard, Nevada County Cannabis Compliance, Placer County Sheriff’s Office, California Regional Water Quality Control Board and the Nevada County District Attorney’s Office.