The Fresno County Sheriff's Office says CAL FIRE Fresno County personnel on a boat spotted the boy against a tree beneath the water Monday.
[Ads /]
The child was nearly two miles downstream from where he initially went in the river Sunday afternoon. A firefighter went into the water and recovered his body.
His sister's body was found near Pine Flat Dam in Fresno County an hour after being reported missing.
Authorities say the siblings disappeared after their mother and a friend tried to take them across the river to a rock. Officials say the children were not wearing life jackets.
The effort to find the children included 40 search and rescue personnel. They used boats on the river, a remote controlled vehicle in the water, plus drones and the sheriff's office helicopter in the air.
Authorities say if parents allow their children in the water, they could face child neglect and child endangerment charges.
Signs have been posted along the Kings and San Joaquin rivers since March 14 urging people to stay out of the water because of hazardous conditions, the sheriff's office said. Warming weather is melting huge amounts of mountain snow that accumulated over the winter.
[Ads /]
"The conditions of our waterways will only become more dangerous heading into summer as snow melts and dams release even more water into the rivers," the sheriff's office said, noting that the water remains cold and currents remain swift.
Farther north, authorities were investigating after a body was found Friday in Folsom Lake northeast of Sacramento. And two people remained missing after being swept away by the American River in recent weeks, the Placer County Sheriff's Office said.
Authorities have warned people to take caution along rivers throughout the state that are experiencing high water levels and stronger flows.
The Associated Press contributed to this report.