Rescuers in inflatable motorboats also searched Monday for bodies near Camp Mystic, an all-girls summer camp, where 27 campers and counselors died after being swept away by floodwaters.

Another team collected the children's belongings from flooded cabins marked by mud lines exceeding five feet (1.5 meters) high.

About 30 volunteers on horseback, many wearing cowboy hats, joined mounted police from Austin to support rescue efforts in four towns along the Guadalupe River in Kerr County.

Michael Duncan, 55, rode Ranger, his dark brown horse, along the river, supporting rescue efforts that have deployed hundreds of searchers along several miles of the waterway.

"Obviously (on horseback)... we can gain more ground. We can get to some areas where people can't get to as easy," Duncan told AFP.

The horses easily navigate the hilly terrain, undergrowth and debris left behind after the rain-swollen floodwaters receded.

Perched atop Ranger, Duncan said that the "height advantage" allowed him to scan across the mounds of debris.

Volunteers on foot also scoured the area, detecting foul odours from undergrowth that could indicate decomposing animals or human remains.

They dug through earth piled near trees, using pointed sticks to probe mounds for any signs of bodies.

During their search, they found children's swimming goggles and a football.

'Emotional debt'

Tom Olson, a rescue dog trainer, deployed his eight-year-old Belgian Malinois, Abby, to assist the search.

Olson, 55, compared the dog's search abilities to a useful tool, "just like underwater sonar boats, drone, aircraft."

"The dog will be able to rapidly find a potential victim... lowering the risk to the people that are out here actually trying to do the search and rescue," he told AFP.

Olson said the work to recover victims' bodies involved "a mental debt" and "emotional debt" but was necessary to bring "closure to the families that lost (people), as well as closure for the rescuers."

Electric company crews also worked to restore power poles and cables destroyed by the floods as the Guadalupe River receded to its normal course.

Duncan, the mounted volunteer, said the searches filled him with "a lot of sadness" but added: "It's also great to see how many people come out... and most everybody is doing this for free.

"That's pretty inspiring to see."