Authorities made more than 20 arrests Wednesday during early morning raids on residences in Lac du Flambeau.
Tribal officials called it "Operation Pandora". More than 40 law enforcement officials from 11 agencies were involved to curtail the use of synthetic and prescription drugs.
Lac du Flambeau Tribal Police Chief Bob Brandenburg said the raids were the first wave of efforts to stop illegal drugs on the reservation.
Tribal Chair Tom Maulson said after a state of emergency was declared in Lac du Flambeau in April they were going to take action.