Chevrolet denied on Friday any knowledge of the IndyCar cheating scandal within Team Penske and said it hired an independent law firm to investigate whether General Motors employees were involved.

General Motors President Mark Reuss said the manufacturer respects the “decision and actions” of IndyCar following last week’s disqualifications of winner Josef Newgarden and Penske teammate Scott McLaughlin from the March 10 season-opening race.

IndyCar nearly two months later discovered that the push-to-pass software system on all three Penske cars had been manipulated to override series rules and allow the drivers to utilize the boost of horsepower during restarts.

IndyCar has not released the data, but reigning Indianapolis 500 winner Newgarden said he used the button improperly three times and assumed because it worked, there had been a change to the rules. McLaughlin, who was stripped of his third-place finish, said he pressed the button once out of habit but gained no on-track advantage.