NASCAR plans to thoroughly examine Kyle Larson's car and the catch fence in its investigation of last week's multi-car crash at Daytona International Speedway, which injured at least 28 race fans in the grandstands.

During a press conference on Saturday at Phoenix International Raceway, NASCAR senior vice president of racing operations Steve O'Donnell provided details of the sanctioning body's ongoing investigation of the incident.

The accident, involving 12 cars, occurred on the frontstretch during the final lap of the 300-mile Nationwide Series race at Daytona. Rookie Kyle Larson flipped around and sailed into the fence before coming back down on the track. Flying debris from Larson's car and the fence struck dozens of spectators. Two people remain hospitalized in a Daytona Beach, Fla. hospital.

The front end of Larson's No. 32 Chevrolet was ripped apart after it tore a gaping hole in the catchfence. The engine and one of the tires sheared off of his car and lodged in the fencing. Another tire from his vehicle flew over the fence, which is 22 feet high, and landed in the upper deck of the grandstands. Neither Larson nor any other driver involved in the incident was injured.

"Based on what happened in Daytona, we met immediately with the folks at Daytona International Speedway and have had multiple meetings this week," O'Donnell said in his opening remarks. "It's truly been a collaborative effort with the goal of doing two things - looking at what happened in this incident, and more importantly, the go forward plan of what we can learn and what we want to implement as we go forward."

Even though the parts from Larson's car have been secured by NASCAR, O'Donnell said that, unlike other incidents, the car remained at the racetrack for personnel at Daytona and experts they have brought in to examine it during their investigation. The vehicle is in the process of being sent to the NASCAR Research and Development Center in Concord, N.C.

When the car arrives there, O'Donnell said NASCAR will first focus on its impact on the fence and learn how the parts were extracted.

"We'll go through each part of the car," he said. "We want to look at how everything held up that was in the car, the cockpit, the tethers. There's been talk if the tethers broke away or not. They did not. When you look at the car, the part that the car was tethered to sheared the car. That's something we have to look at in advance. We've tethered a number of different things and added things to the safety aspects of the car, but what do we need to do in addition to that when we look at this accident specifically."

NASCAR plans to interview members from Larson's team at Turner Scott Motorsports. Since his car was immediately impounded after the incident, the team has not had a chance to examine it. NASCAR wants to find out how the car was constructed and fabricated.

The next step will be the reconstruction of the car. NASCAR will look at all video cameras used during the final lap of the race to help them in this process.

O'Donnell said another aspect of NASCAR's investigation will be examining the fencing. NASCAR plans to use outside experts, including Dr. Dean Sicking, who is the director of the Midwest Roadside Safety Facility and professor at the University of Nebraska-Lincoln. Sicking has worked with NASCAR on many of its safety initiatives in the past.

NASCAR also has a partnership with Indianapolis Motor Speedway, where the Steel and Foam Energy Reduction (SAFER) Barrier came together. Engineering experts on fencing will help in the investigation as well.

"We'll use the best and brightest, and we'll enlist those folks going forward," O'Donnell said. "We think it will validate our findings and find a peer review we can go to.

"Concurrently with all this, Daytona International Speedway is looking at the fencing, bringing in their experts. They're also in the process of bringing in an outside firm to analyze what was in place and look to what we may need to do going forward."

O'Donnell did not give a timetable of when the investigation will be completed. He did mention that the first phase of the probe will look at the restrictor-plate racetracks (Daytona and Talladega Superspeedway). NASCAR will continue its use of restrictor plates on the Nationwide and Sprint Cup Series cars for the unforeseeable future. Both series will race at Talladega the first weekend in May.

The next phase will focus on all other racetracks on the current series schedules.

O'Donnell also gave an update on Michael Annett's accident in the Nationwide race at Daytona, which occurred shortly before the last-lap crash. He said NASCAR is currently examining his car.

Annett suffered a fracture and dislocation of his sternum during the wreck. He underwent surgery and was released from the hospital in North Carolina earlier this week. Aric Almirola is driving his No. 43 Richard Petty Motorsports Ford in the 200-mile race at Phoenix.

"I think we're in a better position than ever to work with Michael, talk about what happened, what he experienced, and the recovery phase, make sure we're in tandem," O'Donnell said. "We'll certainly learn from that. We've learned from every incident we've had. It's never something we want to go through. I think each time we've learned something new to apply to the racecar or the driver safety system."