Stewart's team was forced to prepare a backup car for this weekend's activity. NASCAR president Mike Helton said the defending Winston Cup champion's car did not come close to fitting the template used in technical inspection, calling Stewart's car "exotic."
"The uniqueness behind our action is that there's been a great deal of time spent by NASCAR and the race teams to adapt to the common body location and the new templates," Helton said.
"All the effort by NASCAR Winston Cup director John Darby and his folks has been, along with the cooperation of the teams, designed to eliminate the 'exoticeness' of the cars they were traveling toward.
"This is the first occasion we've had when a car presented for inspection was pretty much out of that box that has been built with the current cars."
The area in question was the rear of the car, which was offset. That part of the car's chassis is known as the "C-post," which is part of the rear deck window. The two sides bulged out at different angles, leading NASCAR officials to confiscate the car.
"The easiest way to sum it up is to say the rear of the car was offset too far to the right," Darby said.
Generally, when a car fails technical inspection, the offending team is allowed to take the car back to the garage area and work on the car to get it to meet the requirements.
"We felt like what we wanted to do was impound the car instead of let (the team) cut it up and try to fix it, even if they might have been able to," Helton said. "It's the area around the back of the car from the rear window to the rear deck. All I can say is it didn't fit the templates and it didn't fit very well at all."
Helton said the car will be impounded and sent for further investigation at NASCAR's Research and Development Center in Concord, N.C.
"The resources at that center give us a greater opportunity to understand things like this," Helton said. "We chose not to give them the option because we want to understand it more.
"Joe Gibbs Racing has been a great proponent of everything we've done in this area and why this car is here, I don't know right now. We simply took the option of fixing it away from them. But there's been a great debate about whether it could have been fixed or not."
Helton said while further repercussions are possible, the fact the car was taken away from the team was a significant statement.
"We've got the car in our possession," Helton said. "They've gone into the qualifying process with their backup car. As the situation unfolds, we may or may not react further."
Stewart said he will not let the infraction affect his ability to compete in Sunday's 500-mile race at the 1.5-mile oval.
"The cars all look the same from where I'm sitting," Stewart said. "I've got three things that I'm in control of -- a steering wheel, the shifter and the pedals. I've got everything I need to do the job I need to do with the car we've got right now. All of our cars are good, whether they are a primary or a backup."
Greg Zipadelli is Stewart's crew chief and tried to explain what may have caused the car to be offset so badly. He said the decision was "just as big a shock to me as it was to the people at NASCAR."
"It is something that they check back on the plates at the race shop as we are building the car," Zipadelli said. "Obviously, they didn't check it close enough. When they put the back window in, it seemed to change the measurement an awful lot.
"There's a rule, so I don't have much to stand on. I'm disappointed with the people at the shop, because it's a measurement that's pretty cut and dry. It's nobody's fault but our own."