Authorities say they've destroyed more than 22,000 marijuana plants being grown illegally on a Northern California American Indian reservation.

The Mendocino County Sheriff’s Office says a raid Tuesday at the Round Valley Indian Reservation found 55 plastic greenhouses. Two people were arrested and eight others were identified and released but could face criminal charges later.

The Sheriff's Office says there's been concern about non-native persons setting up large pot operations on reservation land.

Authorities say there has been an increase in gunfire and acts of intimidation associated with the operations.