A portion of the Dover International Speedway track came apart during Sunday's FedEx 400.
The concrete surface in Turn 2 came dislodged when Ryan Newman ran across the area jostling a chunk that Jamie McMurray then collided with, damaging the nose of his Chevrolet. Concrete also broke a window on a pedestrian crossing bridge overlooking the backstretch. There were no injuries.
NASCAR red flagged the race on Lap 161, allowing track workers to patch the surface using quick dry cement. Officials estimate the pothole at three inches deep, six inches to 10 inches wide.
The race was stopped for 22 minutes. After repairs no further issues were reported.
Inspectors reported no excessive wear on the 1-mile track during a mandatory prerace walk of the speedway, which is just one of two on the circuit comprised solely of concrete. The walking bridge was temporarily closed and repaired using duct tape.
"We do a track walk after every race and in the morning," NASCAR vice president of competition Robin Pemberton said. "At the time there had been a previous patch, but our staff didn't see anything wrong with it."
But the hole was noticeable to several drivers even before the start of Sunday's event.
"When I was coming to the drivers' meeting, I could just see the corner of one of those (concrete) slabs," said race-winner Jimmie Johnson. "I could see something from afar that just looked like the edge was broken, like the corner was broken on it. I didn't think much of it.
"I just chalked it up to maybe a bad angle looking at something, because I didn't drive over the top of it, I saw it from 40, 50 yards away."
Kevin Harvick was leading at the time of the incident. He told FOX he was not surprised about the development saying he was looking at the pothole last night.
"That corner had been knocked out for a while," Harvick said. "I guess it finally worked its way out."
This marks the second time in 10 years a track has come apart during a Sprint Cup race. In 2004 at Martinsville Speedway a piece of asphalt severely damaged the front of Jeff Gordon's Chevrolet, as well during the middle of the 2010 Daytona 500 -- a race won by McMurray.
McMurray's No. 1 team lobbied NASCAR during the red flag to make repairs Sunday, but officials didn't allow it. Crews are only allowed to work on cars during green- and yellow-flag periods and not when the race is stopped.
"When I came off of the corner, it just felt like I hit something obviously heavy," said Jamie McMurray, who hit the piece of concrete. "Initially I thought I'd blown a tire out. When I hit it, it actually pushed the car to the right and I got into the fence a little bit. And as I slowed down, I couldn't figure out first off why I didn't hit the fence harder, and then what happened. I didn't see anything."
NASCAR has made exceptions previously when something out of the ordinary affects a large number of drivers. One such exception was what occurred last year when a TV cable fell onto the track at Charlotte Motor Speedway damaging several cars. The race was stopped and teams were given the opportunity to make repairs.
"Our policy is not to let them work on the car," Pemberton said. "When we had an equipment failure, broadcast equipment failure that affected the entire field of race cars at that time we did red flag and we did allow the teams to fix the damage that was caused by that equipment failure. But that is our normal policy, to not allow teams to work on their cars."