NEW YORK, (AFP) -- Former NASCAR racing champion Tony Stewart hit and killed a driver who left his damaged car mid-race at the Canandaigua Motorsports Park in upstate New York, US media reported Sunday.

ESPN.com said that Stewart, a three-time NASCAR Sprint Cup Series champion, first bumped the victim's car and knocked it out of the late Saturday race.

On his next time around the track Stewart then struck the driver when the victim left his car to confront the NASCAR champion on the dirt track, Ontario County Sheriff Phil Povero told reporters, according to FoxNews.com.

Povero later told US media, including ABC affiliate 13WHAM, that the driver had died but did not identify him.

Fans and witnesses said the victim was Kevin Ward Jr, 20, ESPN said. Videos said to be of the incident posted on YouTube elicited fierce debate over whether Stewart intentionally swerved to hit the driver or not.

The incident happened during an Empire Super Sprints race, which was being held on the eve of a NASCAR race at Watkins Glen International where Stewart was scheduled to compete on Sunday.

The rest of the Empire Super Sprints races were canceled after the incident.

Witnesses said Stewart, 43, did not appear to have been injured. Povero said that police questioned and released him, ESPN said.