Tony Stewart said he's "very embarrassed" about his confrontation with a with a track owner in Australia that led to questioning at a police station.

The dispute at Sydney Speedway last week was over track conditions that the two-time NASCAR champion deemed unsafe. Stewart called the matter an "altercation," and several Australian racing websites reported he fought with speedway co-owner Brett Morris.

"We'd been over there almost five weeks and had the same problem with the race track," Stewart said Thursday. "It wasn't something that was just one incident. I've always been one to speak up for what I think is right, especially when it comes to the safety side of it. I didn't think the conditions were safe to run on, and they felt differently."

New South Wales state police said last week that police were called. Spokesperson Joanne Elliott said a 39-year-old man was arrested at the scene after a 46-year-old man was allegedly hit in the face by a racing helmet. The younger man was released without charge, pending further investigation.

Stewart, who is 39, said he could face more questions from Australian police.

"I've lost a lot of sleep over it," he said. "I am very embarrassed that I made it through a whole trip, and the night before I come home, I get into an altercation with somebody. That really hasn't happened for a while. I am not at all proud of it, I am ashamed about it."

Stewart said he's glad to be back in his No. 14 Chevrolet and with his race team at Daytona International Speedway. The track opened Thursday for three days of testing leading into next month's season-opening race.