CHICAGO • The authorities in the US state of Kansas are investigating the death of a 10-year-old boy when he was taking a ride on what is billed as the world's tallest water slide.

Caleb Thomas Schwab, the son of a state lawmaker, died on Sunday while riding on the Verruckt, a towering water slide at the Schlitterbahn water park that sends riders plunging down from a height of about 17 storeys, at up to 80kmh.

He was riding with two women on a raft, police said. Officials rushed to the scene after a report of an emergency and found the boy "dead from a fatal neck injury, at the end of the ride, in the pool".

The Kansas City Star newspaper said the park was teeming with children of legislators and their parents - they were enjoying free passes - when the accident occurred.

The Verruckt, which means "insane" in German, opened in July 2014, after delays of more than a month due to technical problems.

At the time, Kansas City TV station KCTV reported that the park said the ride was "not behaving properly", after which netting was added around the slide.

The boy is the son of Representative Scott Schwab, a Republican from Kansas, and his wife Michele. "Since the day he was born, he brought abundant joy to our family and all those who he came into contact with," a family statement said.

"As we try to mend our home with him no longer with us, we are comforted knowing he believed in his saviour, Jesus, and they are forever together now ."

A park website description of the water slide said two to three people are typically strapped to a raft and then sent down a "jaw-dropping" 51.4m slide. They are then "blasted back up a second massive hill, and then sent down yet another gut-wrenching drop for the ultimate in water slide thrills".

Those going on the slide are required to be at least 1.37m tall.

AGENCE FRANCE-PRESSE, REUTERS