A 20-year-old racing driver has died after an incident during a regional sprint car event at Canandaigua Motorsports Park that involved three-time NASCAR Cup champion Tony Stewart.

Kevin Ward Jr. was competing in the Lucas Oil SuperSprint Feature race at the half-mile dirt track north of Syracuse in upstate New York on Saturday night when he crashed while fighting for position with Stewart. The Cup star had apparently squeezed Ward into the outside wall at the exit of turn 2 in a typical sprint racing move.

Ward climbed out of his car following the initial accident, but stayed on the race track on foot seemingly to signal his displeasure and remonstrate with Stewart over their clash. Ward was wearing black overalls and a black helmet on a dimly-lit track as he walked back down to the racing line. As Stewart neared the scene under yellow flags, he was running side-by-side with another competitor and ended up striking Ward.

"[Ward] got out of the car after the caution was thrown and began to walk down the track, pointing right at the #14, throwing his hands all around," sprint car racer and eyewitness Tyler Graves told USA Today. "The last thing I seen Kevin do was put his finger to his helmet.

"[Stewart's car] set sideways, the right rear tyre hit Kevin, Kevin was sucked underneath and was stuck under it for a second or two and then it threw him about 50 yards," Graves added.

There had been suggestions that Stewart had revved his engine just before the collision, perhaps to signal his response to Ward's remonstrations, but Graves told Sporting News that he didn't think there had been anything intentional about the accident.

"You never mean to do something like that," Graves said. "Kevin was pissed and he let Tony know. And Tony was trying to give the message back that he wasn't happy either."

Ward was immediately attended by medical staff and transported to a local hospital, but he was reported as being dead on arrival.

Race activity at Canandaigua was immediately cancelled for the night, and an official investigation into the incident was launched by the local sheriff's office and the district attorney. Officers examined Stewart's car in the pit area and were present around Stewart's hauler long after the remaining teams had left the facility.

"This is an ongoing investigation of an on-track crash," confirmed Ontario County (NY) Sheriff Philip C Povero, who said that Stewart was "very upset" over what had happened.

Povero added that the death was not being treated as a criminal matter at this time and that there was no question of Stewart being arrested or detained. "Mr Stewart has cooperated with the investigation, which is ongoing."

A spokesman for Stewart's NASCAR Sprint Cup race team released a short statement overnight confirming the events.

"A tragic accident took place last night during a sprint car race in which Tony Stewart was participating," said Mike Arning. "Tony was unhurt, but a fellow competitor lost his life. Our thoughts and prayers go out to his family and friends. We're still attempting to sort through all the details and we appreciate your understanding during this difficult time."

NASCAR did not issue any statement regarding the incident, and the racetrack said that it would not be officially commenting at this time.

"Canandaigua Motorspots Park will not have an official statement on the accident that happened in the ESS race until tomorrow. Please pray for the entire racing community of fans, drivers, and families. Please be respectful in any comments."

Stewart had only just returned to sprint car short track racing after almost a full year away following the accident in August 2013 that left him with multiple fractures to his right leg and forced him to sit out the remainder of last year's NASCAR Sprint Cup competition. The month prior to that accident, Stewart had been involved in an incident at Canandaigua in which he inadvertently triggered a multi-car wreck that sent two other drivers to hospital with injuries, including one 19-year-old who suffered a compression fracture to her back.

Despite Saturday night's fatal accident, Stewart is still expected to take part in Sunday afternoon's NASCAR Sprint Cup race at Watkins Glen International, which is located about an hour's drive away from Canandaigua.

Kevin Ward Jr. from Lyons Falls, New York was four when he began racing go-karts, and went on to win six track championships and around 250 races in eight years of competition. He moved on to micro sprint racing in 2007 and won championships in 2008 and 2009 before graduating to sprint racing in 2010. He was listed as seventh in the points in the current Empire Super Sprints standings, with two top-five finishes and four top-10 results as of July 21.

The official summary report from the Ontario County Sheriff's Office reads in full:

"On Saturday, August 9, 2014, at or about 10:30pm there was an on track incident at the exit of turn 2 at the Canandaigua Motorsports Park during the Lucas Oil SuperSprint Feature race. The race was in lap 14 of a 25 lap race when one car lost control and spun coming to rest along the outside retaining wall.

"The race was immediately put into caution, slowing the cars on the track. The driver of the car that spun exited the race car and walked down the track onto the racing surface. Two racecars travelling in tandem approached as the driver continued down the track, gesturing to the two approaching cars. The first car swerved to avoid the driver out on track. The second car, operated by Tony Stewart, struck the driver.

"The driver was treated by on track medical staff and was transported to FF Thompson Hospital where he was pronounced deceased at 11:15pm.

"At this point, Mr Stewart has cooperated with the investigation which is ongoing. The Sheriff's Office has asked the individuals who possess amateur video to please contact with this office so that copies of the video accounts can be obtained for review."