"Unfortunately, a member of our raceway family here, a fan, has passed away," he said.
The Pennsylvania 400 was called because of storms, with 98 of the 160 scheduled laps completed. As the storm approached, the track posted messages on its Twitter page to more than 22,000 followers near the end of the race encouraging fans to "seek shelter as severe lightning and heavy winds are in our area."
The attendance was estimated by the track at 85,000. Pocono spokesman Bob Pleban said public address announcements were made before the storm and the end of the race for fans to take shelter and evacuate the grandstands.
Racetrack officials were reviewing the logs of when the announcements were made, Pleban said. There was no order to evacuate the track premises.
Jeff 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, Pleban said. The other five people were taken to various hospitals with minor to moderate injuries, he said.
"We are deeply saddened that a fan has died and others were injured by lightning strikes following today's race at Pocono," NASCAR spokesman David Higdon said. "Our thoughts are with them as well as those affected by this unfortunate accident."