Graham Rahal was placed on probation for six races by IndyCar on Tuesday for his role in an accident with Marco Andretti.

Reviews showed Rahal was guilty of blocking and initiating avoidable contact Sunday on Lap 22 at Long Beach, IndyCar race director Beaux Barfield said. Andretti's car hit the back of Rahal's, launched briefly into the air and spun into a tire barrier.

Andretti said Rahal chopped him, adding: "I'm lucky I didn't get upside down. I could have been killed."

Barfield and his team did not review the accident until they returned to Indianapolis because both cars were knocked out of the race and it wasn't a pressing matter.

"All stewards have reviewed the incident and have decided that the on-track actions of Graham warranted probation because of driving that endangers on-track safety and adversely affects competition," Barfield said in issuing the penalty.

The probation runs through IndyCar's June 23 race at Iowa Speedway. The penalty notice on Rahal said, "If the improvements are not met, IndyCar may impose other penalties at its discretions."

The IndyCar rule book states that a driver must not alter their racing line to inhibit or prevent passing, and the penalty is a minimum of a black flag "drive through" penalty. The rules also state a driver must not initiate or attempt to initiate avoidable contact that results in the interruption of another competitor's lap time or track position.

Rahal and Andretti declined comment Tuesday through their race teams.

But after the race Sunday, Rahal denied chopping in front of Andretti.

"By the rules, you're allowed to make one move. I made one move," he said. "At the speed he hit me at, he wouldn't have made the corner. It broke my gearbox, that's how hard he hit me. If we had just run wheel to wheel it would never, ever have been that bad. But the rate of speed that he was carrying, he wasn't going to make it. Plus at that corner at that time, I was protecting my line to the right, which I'm allowed to do by the rules."

When asked about Andretti's claim he'd been chopped, Rahal intimated that Andretti seldom takes responsibility for mistakes on the track.

"What's Marco's last name?" Rahal asked. "I've said enough."

That triggered a brief commotion on Monday when racing great Mario Andretti, the drivers' grandfather, asked Rahal on Twitter if he had a problem. Rahal replied he'd prefer to talk to Mario Andretti rather than have a discussion on Twitter.

Andretti replied with a tweet referencing the quote about Marco's last name, adding: "That insult includes me. You insulted me to the world & I responded."

The two spoke by phone on Tuesday and both posted on Twitter that everything was fine between them. Rahal had previously tweeted he had also spoken with Marco Andretti.