updated 7:52 p.m. ET Feb. 11, 2007

DAYTONA BEACH, Fla. - Matt Kenseth and Kasey Kahne failed inspection after qualifying Sunday for the Daytona 500, and their teams could face harsh penalties before NASCAR’s season opener.

Their qualifying times were disallowed after inspectors discovered illegal modifications in each car. NASCAR said Kenseth’s Ford had illegal holes in the wheel well and Kahne’s Dodge also had illegal holes in an unspecified location. The holes may have improved the aerodynamics of their cars.

It’s the second consecutive year NASCAR discovered violations following pole qualifying. Last year, crew chief Chad Knaus was thrown out of the race after Jimmie Johnson’s car failed inspection. Knaus was suspended four races. Johnson rebounded to win the Daytona 500 the following week and they eventually reunited and won the Nextel Cup championship.

“We are committed to try to stop all the games being played,” NASCAR spokesman Jim Hunter said. “Obviously, the parties involved are going to have to tell the story however they want to tell it. But NASCAR is charged with maintaining the integrity in that garage area and we’re going to do whatever we need to do to do it.”

Hunter said NASCAR officials were planning to discuss the situation Sunday night, and that penalties could be expected Monday or Tuesday.

Michael Waltrip’s car also was impounded after inspectors found a questionable substance inside the intake manifold. Waltrip was allowed to replace the manifold and qualify, but then the car was taken so NASCAR could go through it with “a fine tooth comb.”

Kenseth, the 2003 Cup champion and last year’s runner-up, and Kahne, who finished eighth last season, will be allowed in the qualifying races Thursday. But they will have to start from the back of the pack in the second 150-mile race.

“I am surprised, but at the same token, our inspection process gets better every year,” Hunter said.