DAYTONA BEACH, Fla. — At least 28 people were injured in a crash at the end of a Nascar race at Daytona International Speedway on Saturday afternoon, bringing the issue of safety at racetracks back to the forefront on the eve of Sunday’s season-opening showcase, the Daytona 500.

Byron Cogdell, a spokesman at Halifax Health Medical Center, confirmed that seven people were being treated there for injuries caused by debris that flew into the stands, with two of them in critical condition, including one child.

Cogdell also said the Halifax Health Medical Center of Port Orange was treating six more of the injured, with those in stable condition. Another was being treated at Florida Hospital Memorial Medical Center in Daytona Beach.

The Daytona International Speedway president, Joie Chitwood, said 14 people were transported to various hospitals, with another 14 treated at an infield care center at the track.

The injuries occurred after a 12-car crash as the field approached the checkered flag at the end of a Nationwide Series race won by Tony Stewart. The No. 32 car driven by the rookie Kyle Larson went airborne in the wreck and hit the catch-fence that surrounds the track and is designed to protect fans. The entire front end of Larson’s racecar was sheared off, and debris from the car, including two tires, flew into the stands. The engine wound up in a hole in the catch-fence.

“First and foremost, our thoughts and prayers are with our race fans,” Chitwood said. “On the incident, we responded appropriately according to our protocols and had emergency medical personnel at the incident immediately.

“We’re in the process of preparing the facility and will be ready to go racing tomorrow.”

There were no injuries among the 12 drivers involved in the crash, including the stars Dale Earnhardt Jr. and Brad Keselowski, the 2012 Sprint Cup champion. All were examined at the infield care center and released.

The Daytona police would not release any information on the crash and referred all media inquiries to public relations officials at the speedway, who did not comment.

The crash came as Nascar was primed for its most anticipated season-opening Daytona 500 in years, with Danica Patrick set to become the first woman to start a Sprint Cup race from the pole position and a fleet of new racecars making its debut.

Daytona International Speedway was the site of Nascar’s darkest hour 12 years ago, when the seven-time Cup champion Dale Earnhardt was killed in a crash on the final lap of the 2001 Daytona 500. Safety initiatives followed the crash, and no other driver has been killed in a Nascar national series race since then.

But there have been other serious crashes, including incidents in which racecars have gone airborne. In April 2009, the car driven by Carl Edwards left the track and hit the catch-fence at Talladega Superspeedway in Alabama. Seven fans were injured, including one who sustained a broken jaw.

Ryan Newman’s racecar also went airborne during a race at Talladega in the fall of 2009. Nascar has worked on improving roof flaps to prevent cars lifting off the racing surface in a crash.

The IndyCar driver Dan Wheldon was killed when his open-wheel racecar went airborne in a crash at Las Vegas Motor Speedway in 2011.

In a Twitter post on Saturday, another IndyCar driver, Dario Franchitti, implored IndyCar and Nascar officials to do something about catch-fences. Franchitti wrote: “It’s time @indycar @nascar other sanctioning bodies & promoters work on an alternative to catch fencing. There has to be a better solution.” He added: “@indycar @nascar give the engineers and scientists a budget and they’ll find a fix. They did it with the safer barrier.”

The Safer barrier is a wall that absorbs energy in a crash and was installed at tracks after Earnhardt’s death.

“We’re really early in what we’ve seen,” Steve O’Donnell, Nascar’s senior vice president for racing operations, said in a news conference at the speedway Saturday night. “Some of the things we have in place, tethers, that sort of thing, held up, did their job. But certainly when you look at this incident, there are some things we can learn and evaluate. We’ll take the car, we’ll do that. We’ll evaluate the fencing and see if there’s anything we can learn from where gates are.”
Nascar’s senior vice president and chief marketing officer, Steve Phelps, confirmed that Nascar moved to block a video of the crash and victims in the stands that was posted to YouTube after the race.

The video, shot by a fan in a section of the grandstands where the accident occurred, captured the mayhem that followed. The stands in several sections were filled with smoke from the burning cars. Fans were seen waving frantically to get medical help, and one man removed his shirt to assist an injured fan.

Saturday’s accident occurred at the front of the pack of racecars as they rounded Turn 4 and headed toward the finish line. Regan Smith, driving the No. 7, was leading and was being pushed by Keselowski. As they approached the end, Keselowski attempted to pass Smith, but Smith blocked him from trying to get to the outside. That led to the crash at the front of the pack that collected 12 racecars in all. Larson was hit by several cars when his car went into the air.

“I was getting pushed from behind, I felt like, and by the time my spotter said lift or go low, it was too late,” Larson said. “I was in the wreck and then felt like it was slowing down and I looked like I could see the ground. Had some flames come in the cockpit, but luckily I was all right and could get out of the car quick.”

As for the cause of the crash, Smith took the blame.

“I tried to throw a block coming off of 4,” he said. “I knew Brad was going to go make a move. It’s Daytona; you want to go for the win here.”

Keselowski said he was going for the win, too.

“We made a move to try and win the race,” Keselowski said. “I kind of had the run and the move to win the race, and Regan obviously tried to block it, and that’s understandable. He wants to win, too, and at the end it just caused chaos. There was obviously a big wreck with a lot of debris and cars torn up. I really hope everyone in the grandstands is O.K. I think that’s the most important thing right now.”

There was a brief, muted ceremony in victory lane as emergency workers continued to tend to the injured.

“The important thing is what’s going on on the front stretch right now,” Stewart said. “We’ve always known since racing was started this is a dangerous sport. But it’s hard. We assume that risk. It’s hard when the fans get caught up in it. As much as we wanted to celebrate right now, as much as this is a big deal to us, I’m more worried about the drivers and fans in the stands right now. I could see it all in the mirror and it didn’t look good from where I was, either.”