Sgt. Brandon Jones of the Maricopa County Sheriff's Office made the announcement Wednesday morning, but did not elaborate. More details were expected later in the day.
Crews have spent the last few days searching the river for Joshua Williams. The 21-year-old disappeared while tubing with friends Sunday evening. Deputies say Williams vanished as the group went around a curve in the river.
Jones said it's likely the body found Wednesday is that of Williams, but investigators have not yet confirmed it.
Coon Bluff, which is about 17 miles northeast of Mesa, is a popular river-access point for tubers. It's not clear how far that is from where Williams was last seen.