BULLHEAD CITY, Ariz. — Authorities in western Arizona have found the body of an 8-year-old nonverbal autistic boy who had gone missing.

A kayaker notified Bullhead City authorities early Sunday after coming across the child's body in the Colorado River.

Bullhead City Police Chief Brian Williamson confirmed later Sunday morning that the remains were those of Jeremy Duncan, who went missing Saturday morning.

More than 1,000 first responders and volunteers searched by land, air and water for the boy into the nighttime hours. They included people on horseback, police with specially trained dogs, and rescuers in boats on the river.

During a news conference, Williamson thanked the hundreds of people who participated in the search. He added that the circumstances of the apparent drowning are being investigated.