(CNN) - A Florida state agency said Friday it has opened a probe to find out why a roller coaster derailed at an amusement park Thursday night in Daytona Beach.
The accident sent two riders plunging 34 feet to the ground and left two others dangling in one of the ride's cars, the Daytona Beach Fire Department said. They were among 10 people on the Sand Blaster ride at the Daytona Beach Boardwalk.
"First and foremost, we're concerned about the individuals who were injured last night. Their well-being and recovery is of the utmost importance," said Jennifer Meale, spokeswoman for the state's Department of Agriculture and Consumer Services.
Meale said the ride had passed inspection the morning of the accident. It was inspected again after the accident and failed due to deficiency listed as "structural integrity: other."
She said the ride failed two previous inspections in May due to multiple deficiencies, but all of the problems had been corrected before Thursday's accident.
"We have launched an investigation to determine the cause of the accident, and anyone who should be held accountable will be held accountable," she said.
After the accident, responders raced to the scene, working to keep the dangling car from falling. They plucked the two riders from it and brought them and the others to safety.
"Firefighters had to get ladders on the ground. We have a tech rescue team specializing in high-rise rescues," fire department spokeswoman Sasha Staton told CNN on Friday. "They were the ones that successfully removed the two dangling riders to the ground."
Four riders -- all of whom were on the same car -- and two others were rushed to Halifax Health Medical Center in Daytona Beach. A hospital official said information about their condition might be released sometime Friday.
Later Friday, the hospital said it "received nine patients."
"It was definitely chaotic and time-sensitive," Staton said. "We didn't want the dangling car to fall any further."
Police kept "many bystanders from all directions far enough away for their own safety because we had a lot of equipment and for the firefighters' safety so they'd have plenty of room to work and evacuate the riders," Staton said.
The Daytona Beach Fire Department posted images and videos on its Twitter account of the scene. One of the videos showed stranded riders being rescued by ladder.
According to The Daytona Beach News-Journal, the Sand Blaster has been operating at Daytona Beach since 2013 after the 40-year-old ride was bought from a closed amusement park in Delaware a year earlier.
CNN has contacted the Daytona Beach Boardwalk and the ride's owner for comment.
Michael D'Aquino, a US Department of Labor spokesman, said the Occupational Safety and Health Administration isn't investigating the incident since no employees were injured.
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