Four people remained hospitalized with serious injuries Sunday, including a 10-year-old taken to Children’s Hospital in New Orleans, after the collapse of a Warrior Dash obstacle in St. Francisville on Saturday afternoon.

Brant Thompson, deputy chief with the state Fire Marshal’s Office, said investigators were working to obtain blueprints for all the obstacles in the 5k event and compare them to the structures built on-site at the West Feliciana Sports Park to see if construction practices matched up with the design plans.

“In this case, it appears that the construction method was woefully inadequate, not only to support the structure itself but also the added weight of all the participants,” Thompson said of the wooden “Diesel Dome” that collapsed around 1:30 p.m. Saturday.

Warrior Dash races are held in cities around the country and feature several obstacles, including ponds, mud and large objects that participants must climb and crawl over. The races are organized by Red Frog Events, of Chicago.

More than 5,000 people had registered for the St. Francisville event, and possibly thousands had already traversed the dome before it swayed to the side and slowly crashed to the ground, carrying 20 to 30 people with it, Thompson said.

The number of injuries remained unclear Sunday, but 12 people were taken by ambulance or helicopter to area hospitals with broken bones, lacerations, back and neck injuries, Thompson said. Others were treated on-site or drove themselves to seek treatment.

“We’re still making attempts to contact all of those injured and do interviews with those folks,” he said. “We’ve also requested information from the hospitals where they were treated.”

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Thompson said investigators had received numerous reports from event participants who said the Diesel Dome was showing signs of instability – “wobbling a bit” – while they climbed over it earlier in the day.

“It’s unfortunate that someone with authority was not there making those same observations, someone who could’ve stepped in and discontinued the use of that obstacle,” Thompson said. “It’s unclear whether it was reported to any of the event organizers or their staff. That’s something we’ll seek to determine in the coming days.”

Investigators began marking, painting, photographing and disassembling the collapsed portion of the dome on Saturday, as well as examining several other wooden obstacles on-site.

“Unfortunately, they had taken down some of the obstacles prior to our arrival,” Thompson said. “It seems to be the practice of the organization: as soon as the race is over, they begin disassembling them so they can turn the property over to the owners. Fortunately, we were able to stop them in the process.”

The structures will be compared to the plans architects and engineers designed for the event organizer.

“The expectation when you participate is that conditions will be safe as long as you follow the instructions provided and the rules of the game or the race,” Thompson said. “In this case, it appears that these participants were doing exactly what they should have been doing. It’s not a situation where a group, in a celebratory fashion, was overloading and jumping on the structure. They were simply traversing it as expected. And that’s particularly disturbing to us, that this would happen under those circumstances.”

Investigators also will research whether similar incidents have happened in other states, he said. Saturday’s Warrior Dash was the fourth such event to be held at the West Feliciana Sports Park.