A 10-year-old boy killed during a ride on the world's tallest waterslide was decapitated in the accident, a person familiar with the investigation has said.
Authorities have yet to explain how Sunday's accident in which Caleb Schwab was killed on the Verruckt raft ride at the Schlitterbahn Water Park in Kansas City, Kansas, happened.
Two women who were not family members were also in the raft at the time and were treated for facial injuries.
Caleb's parents, Republican state congressman Scott Schwab and his wife Michele, have not spoken publicly since his death. His funeral will be held on Friday.
Verruckt, German for "insane", featured multi-person rafts that make a 51m drop at speeds of up to 70mph, followed by a surge up a hump and a 15 metre descent to a finishing pool.
Since the accident, investigators have removed netting that was held in place by supports above the 15m section from the hump to the finishing pool.
Riders, who must be at least 1.3m tall, were harnessed with two nylon seat belt-like straps - one that crossed the rider's lap, the other stretching diagonally across the shoulder. Each strap was held in place by long Velcro-style straps rather than buckles. Riders would hold ropes inside the raft.
The park reopened yesterday except for a large section that includes the waterslide, although its towering profile greeted visitors when they drove through the entrance. Access to the Verruckt was blocked by a wooden fence.
On a hot, mid-week day, the park was doing a steady business although there were no queues for other rides.
Schlitterbahn spokeswoman Winter Prosapio said the company was not discussing Sunday's tragedy out of respect for the family. She also said that she could not offer an immediate perspective about how Wednesday's turnout compared with typical attendance.
"We didn't know if we'd get five people, 15 people. But this is affirming," she said.
Sara Craig, 42, said she was slightly uneasy bringing her 14-year-old son Cale and one of his 13-year-old friends to the reopened park.
"I feel guilty having fun when a family is hurting so badly," she said.
She said her family rode Verruckt twice in one day a couple of weeks ago. She remembered a short video they were required to watch, but did not recall it including any caveats about danger.
Ms Craig said that during her first trip down the ride with her son and one of his friends, her shoulder restraint came off, something she opted not to report to park workers.
I didn't think much about it," she said. "You don't think you're going to die.
"I didn't think much about it," she said. "You don't think you're going to die."
They rode it again, only to see the restraint on her son's friend also come loose by the time it was over.
She said the ride's operators sent them down the slide even though their combined weight was 393lbs - shy of the 400lb weight minimum the park advertises as a requirement.
Ms Craig described the ride as "very, very rough", so much so that "when I got off, my head hurt".
The water park passed a private inspection in June that included Verruckt, according to a document released by a Kansas state agency.
A copy of an insurance company inspector's letter on June 7, provided by the Kansas Department of Labour to the Associated Press, said inspections had been completed.
The letter said all rides met guidelines for being insured with "no disqualifying conditions noted".
But it added: "This survey reflects the conditions observed or found at the time of the inspection only, and does not certify safety or integrity of the rides and attractions, physical operations or management practices at any time in the future."
Kansas law requires rides to be inspected annually by the parks, and the state randomly audits the records. The last records audit for Schlitterbahn was June 2012.
Ken Martin, a Richmond, Virginia-based amusement park safety consultant, questioned whether the straps were appropriate, suggesting that a more solid restraint system that fitted over the body, similar to those used in rollercoasters, may have been better.
In early tests, rafts carrying sandbags flew off the slide, prompting engineers to tear down half the ride and reconfigure some angles. A promotional video about building the slide includes footage of two men riding a raft down a half-size test model and going slightly airborne as it crests the top of the first big hill.
Jon Rust, a professor of textile engineering at North Carolina State University, said the material used on the straps, commonly called hook and loop, was not designed to keep a person in the seat. It also can degrade with use.