Ferrari's Sebastian Vettel says he had no previous warning over the tyre failure which brought his Austrian Grand Prix to a premature end.
Vettel started from ninth place on the grid on the Super Soft tyres but stayed out and inherited the lead, when his right rear tyre failed as he began his 25th lap.
Vettel was pitched into the barriers along the pit straight and into retirement, the third time he has failed to reach the chequered flag this season.
"When the rear right tyre failed, I didn't feel anything, or rather, I felt it when it was too late and it exploded out of the blue," he said.
"There were no signes before that, everything was normal. I spoke with the people on the pit-wall and everything looked the same, the pace was the same as the lap before, the tyres felt fine, the lap times were fine.
"It's completely a question mark on why the tyre had the failure."
Vettel added that he did not believe Ferrari's strategy was overly aggressive.
"Obviously the idea was to go on as long as possible with that set of tyres and to shape our race on that idea," he said.
"But I don't think it was an aggressive strategy, as lots of people went longer than us on the same tyres."