Officials at Pocono Raceway say one person is dead and nine are injured after a lightning strike in the parking lot behind the grandstand after a race.
NASCAR officials say two people were taken to hospitals in critical condition after Sunday's lightning strike.
Track president Brandon Igdalsky confirms that one of them later died at Pocono Medical Center.
"Unfortunately, a member of our raceway family here, a fan, has passed away," he said.
Track vice president Bob Pleban says five people were treated at the scene.
Three others were hospitalized with moderate or minor injuries.
Pleban says it's not clear if all 10 were actually struck by lightning. It's unknown whether one or multiple lightning strikes occurred.
eff Gordon, who won the race, said he could hear a huge crack as he walked down the pit road during the storm. "You could tell it was very close," he said. "I mean, that's the thing that's going to take away from the victory, is the fact that somebody was affected by that."
One person remained hospitalized in critical condition at Lehigh Valley Hospital Center, said Bob Pleban, a track spokesman. The other five people were taken to various hospitals with minor to moderate injuries, he said.
"Certainly our thoughts are with them," Gordon said. "I hope everything is OK there."
The track posted warnings on its Twitter page near the end of the race encouraging fans to "seek shelter as severe lightning and heavy winds are in our area."
The race was called off because of rain, with 98 of the 160 scheduled laps completed.