NASCAR fined 2012 NASCAR Sprint Cup champion Brad Keselowski $50,000 and three-time champion Tony Stewart $25,000, and placed both drivers on four-week probation for actions detrimental to stock car racing and in a behavioral penalty for their roles in a post-race fracas at Saturday's Bank of America 500 at Charlotte Motor Speedway.

"These penalties are about maintaining a safe environment following the race," Robin Pemberton, NASCAR senior vice president, competition and racing development, said in a statement. "We knew that the new Chase format was likely going to raise the intensity level and we want our drivers to continue to be themselves. However, the safety of our drivers, crew members, officials, and workers is paramount and we will react when that safety could be compromised."

Keselowski tried, but failed, to spin Denny Hamlin, after Hamlin braked-checked him, and later hit Matt Kenseth's car. Stewart backed his car into Keselowski's, crumpling the front. 

Sporting News reported Hamlin's crew had to restrain him from going after Keselowski in the garage area. Kenseth, however, got his licks in, putting Keselowski into a headlock before onlookers intervened. Keselowski said he retaliated because Kenseth hit him while he was under caution and then was hit by Hamlin afterward.

Hamlin and Kenseth were not fined.

“Those guys can dish it out, but they can’t take it. I gave it back to them and now they want to fight, so I don’t know what’s up with that,” Keselowski said on Saturday.

Stewart did not qualifying for the Chase for the Sprint Cup championship. The 43-year-old didn't compete in three races in August after he struck and killed Kevin Ward Jr. at a track in upstate New York. Stewart was not charged with criminal wrongdoing for the incident.