A wooden dome used as a climbing obstacle in a race collapsed Saturday in St. Francisville, injuring several people and prompting the State Fire Marshal's Office to investigate if the structure was properly built.

Witnesses said there were between 20 and 30 people on the dome, the third of 12 obstacles of the Warrior Dash obstacle race, when it swayed to the side and slowly crashed to the ground.

Justin Cox, operations manager for Acadian Ambulance, said three patients were airlifted and seven more were taken to the hospital in ambulances from the event site at the West Feliciana Sports Park. He said at least 10 to 15 others were injured and drove themselves to seek treatment.

"The range of injuries were from minor to serious," Cox said.

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.

West Feliciana Parish Sheriff Austin Daniel said about 5,500 people participated in Saturday's event.

"It was a major deal," Daniel said by phone from the sports park. "They were climbing on something ... and it collapsed with a gang of people on it. I think they said the worst injury was a broken femur and a head injury, but nothing life threatening."

The obstacle that collapsed is called the Diesel Dome, said Lauren King, Warrior Dash director of public relations. It is promoted on the race's website as a 30-by-50-foot wooden dome "with views of the ground that will ignite your vertigo."

"Our thoughts are with the injured participants and their families," King said in a prepared statement. "The safety and security of our racers and spectators are paramount at our events. We are currently evaluating the situation."

Investigators with the State Fire Marshal's office, West Feliciana Parish Fire Department and West Feliciana Sheriff's Office could be seen surveying the flattened wooden dome Saturday afternoon.

Jason Phillips, of Jena, who said he was competing in his “first and my last” Warrior Dash, hurt his right ankle when the Diesel Dome fell. His leg was wrapped with a bandage and stabilized with a splint.

“People were telling us all day long there was something wrong with it, that it was unsound,” he said.

Phillips said the structure started leaning, then slowly collapsed to the left. It took 10 to 15 minutes for those injured to get treatment, he said, “because nobody from the event staff knew anything was wrong."

Brandi Taylor, also of Jena, said she had a fracture in her left arm below her elbow and sprained her wrist.

“I was climbing to the top of it when it started leaning and collapsed," said Taylor, whose arm was wrapped with a splint and secured against her body. "It was obvious that it was structurally unsound. It was very scary because it happened in slow motion.”

Taylor, a nurse, said she helped some people who had lacerations and what looked to be broken bones.

West Feliciana Parish President Kevin Couhig said Red Frog Events rents out the parish-owned sports park for the Warrior Dash and brings in their own engineers to construct the obstacles.

"They’re responsible for any permitting that is necessary," Couhig said. "The parish does not provide permits for the structures.”

State Fire Marshal Butch Browning said his investigators will meet about the incident in the next week and write a report.

“This is a tragic accident because of the numbers of people who were injured," Browning said. "Our role is to gather the facts, investigate what happened, vet how the structure was constructed and see if there was any permitting necessary.”

“I know our office didn’t permit it," he added.

Browning said the district attorney will be brought in if his office's investigation reveals "something was negligent or something criminal took place."

"People were just looking to have a good time," he said. "I couldn’t imagine how severe it could have been if the structure was any taller.”