NASCAR conceded Monday that water got into the fuel supply of more than two cars during the race at Atlanta Motor Speedway, apparently leading to a crash that took out several top contenders in the closing laps. Denny Hamlin was leading the Pep Boys Auto 500 with three laps to go when his car stalled while taking the green flag after a caution period. Martin Truex, who led the most laps Sunday, smashed into the back of Hamlin's car and finished 31st. Hamlin slipped to 24th. "There are multiple teams that are showing positive for some level of water contamination level in their fuel," said John Darby, NASCAR's Nextel Cup director. "I can't tell you the exact number. It's more than two and less than 43 at the moment."

Darby dismissed sabotage as a possible explanation, saying too many teams were affected for anyone to have been singled out.

"For those who have their evil, twisted conspiracy hats on, we want to put that to rest," Darby said. "If it was sabotage, it would have to be the kind of thing where someone hates NASCAR racing across the board."

He said extensive testing done by Sunoco, NASCAR's official fuel supplier, showed no signs of problems in the underground storage tanks at the suburban Atlanta speedway. The problem likely occurred in the piping that runs from the tanks to the pumps, or in the pumps themselves.

"It's a brownish-colored water," Darby said. "If it was just water, it would be more clear. That should help us understand if it came from a failed pipe or a failed pump or some other source that allowed it to enter the fuel."

In a "huge majority" of cars that tested positive for water in their fuel systems, the amount was so small that it didn't affect performance. For example, winner Jimmie Johnson had some water in his carburetor during the post-race inspection.

But the amount of water was enough to affect at least two drivers: Hamlin and Dave Blaney, who had performance issues all day and finished 38th, 66 laps behind Johnson.