Drug task force investigators have reported the discovery of 51,000 marijuana plants at five sites in northcentral Washington.

Okanogan County Frank T. Rogers says 30,000 pot plants were removed Tuesday from four sites in the Methow Valley. Three people were arrested at a site near Sun Mountain Lodge in Winthrop.

Meanwhile, Colville tribal police asked for help in finding whoever was growing more than 21,000 marijuana plants on the reservation.

Tribal police were joined by police from Republic and Spokane, Border Patrol and FBI agents and sheriff's deputies from three counties in an eradication effort that began Tuesday. The pot was valued at about $21 million.