A father clung to his son and a tree in a rain-swollen northern Arizona river before losing his grip on the 6-year-old boy, who was swept away by the rushing waters and is presumed dead, a fire chief said.

Searchers spent Friday looking for the boy's body with no success, a day after David and Katrina Baudek of rural Mayer loaded their two children, Jacob and Desiree, into a pickup during a powerful winter storm. They were trying to get Jacob to a hospital because he was sick, authorities said.

The family left their home about 70 miles north of Phoenix and headed out on a dirt road that normally is passable.

Tributaries of the nearby Agua Fria River had already flooded local roads. The Baudeks crossed one of them, then decided travel was too dangerous and turned back. They made it 40 feet across a 50-foot wash when the fast-moving water caught their Chevrolet Avalanche and carried it 20 feet downstream, said Mayer Fire Chief Glenn Brown.

Katrina Baudek escaped to higher ground as her husband moved the two children into the truck's bed for safety.

A witness nearby heard the commotion and threw David Baudek a rope while someone called for help, as storm waters rose and covered the truck's roof, Brown said. Separated by 40 feet of rushing water, rescuers could do nothing but beg for a helicopter — something weather conditions wouldn't allow, he said.

After holding on to both children and the rope for about two hours, the father lost his grip and dove toward the shore. Somehow, possibly with the help of her mother, the girl reached safety on the shore as David Baudek clutched a tree his son.

He lost his grip, and Jacob Baudek was swept away.

"Seeing it, you cannot imagine how he was able to hold on as long as he did," Brown said.

Rescuers were separated from the family by the roaring wash and couldn't reach them until Friday morning. The boy remained missing.

Yavapai County Sheriff's Office spokesman Dwight D'Evelyn said the body could have been carried miles away.

An Arizona Department of Public Safety crew flew over the area Friday where Jacob was last seen and found debris piles that were to be checked for any signs of him, D'Evelyn said. Katrina Baudek's jacket was found farther down river.

Conditions wouldn't have allowed the boy to survive, D'Evelyn said.

"A 6-year-old, depending on his medical condition, would probably be unconscious fairly quickly and not have the knowledge of what to do or how to react and probably couldn't swim," he said. "Even an adult would have a hard time in this situation."