PHOENIX (AP) – Federal officials have announced a joint law enforcement operation targeting drug trafficking on an American Indian reservation in western Arizona.

The U.S. Attorney’s Office announced Thursday that a federal grand jury indicted 17 people in the investigation focused on the Colorado River Indian Tribes’ reservation.

According to the office, charges against those indicted include drug trafficking and conspiracy to commit trafficking.

The office says 11 people have been arrested so far and that additional arrests are expected.

The investigation was led by a task force that includes the La Paz County Sheriff’s Office, the U.S. Border Patrol, the federal Drug Enforcement Administration, and the Colorado River Indian Tribes Police Department.

The Bureau of Indian Affairs, the FBI, the U.S. Marshals Service and the Parker Police Department assisted the investigation.