No charges have been laid, but US law enforcement authorities said on Monday they are continuing their investigation into the fatal accident.
Ontario County Sheriff spokesman Philip Povero told reporters on Monday they are seeking more video footage of the crash as part of their investigation.
"We know at this point that a fatal crash did occur, and we are taking as much time as we can to gather every piece of factual information that may exist that will help us clearly identify the cause of the tragedy," Povero said.
"We are basically trying to see if there are any other video recordings that may have been made on Saturday night that could help us." The incident happened near turn two at the halfway point of a 25-lap Lucas Oil Super Sprint Features dirt race.
Stewart first bumped Ward's car and knocked it out of the race. On his next time around, Stewart's vehicle then collided with Ward, who had gotten out of his car and was walking down the track pointing his finger in the direction of Stewart.
As the car passed by Ward it appeared to rev and then fishtail, hitting Ward and dragging him along the track for several metres.
Ward, of Port Leyden, New York, began competing in Go Kart racing at the age four in 1998. He began sprint car racing in 2010 and won his first career sprint car feature in June 2011.
Stewart has a history of dust-ups with other drivers. Two years ago after a crash he walked onto a track at Bristol Motor Speedway in Tennessee and threw his helmet at Matt Kenseth's car.
When Stewart competed in an event at Canandaigua in July 2013, he caused a crash that involved 15 drivers.
-AAP
