BILLINGS, Mont. (AP) — The Yellowstone County Sheriff's Office has identified a body found in the Yellowstone River as a 15-year-old Utah boy.

Sheriff Mike Linder says the autopsy did not reveal any signs of trauma or indications of foul play in the death of Robert Anthony Thompson. It is unclear how Thompson ended up in the river.

The Billings Gazette reports that Thompson was visiting Billings a week ago with his mother and 13-year-old sister. The family arrived too early to check into the campground where they planned to stay and slept in their vehicle near the Dick Johnston Bridge.

Thompson was reported missing June 25 after he walked barefoot to the river sometime during the night and disappeared.

Boaters on the river found the body Saturday.