Pirelli is still unsure what caused the puncture that put Sebastian Vettel out of the Abu Dhabi Grand Prix on the opening lap.
The Red Bull driver started well from pole position and led into Turn 1, but ran wide onto the kerb exiting the corner; his right-rear tyre deflating instantly and causing him to spin off the track as he moved left for Turn 2.
Pirelli motorsport director Paul Hembery said that it will be extremely difficult to apportion blame until a proper investigation has been conducted on the failure.
"That's always a problem when all you get back is a bag of bits. You're not always guaranteed of getting a clear answer," Hembery said.
"We have the tread back, the sidewalls and the rim, so we'll work with Red Bull to find an explanation for Seb. We do know it was an instant deflation at least, and the most likely cause with such a quick deflation is debris.
"You can tend to rule a lot of things out. You can rule out a number of aspects. It was a used set [of tyres] as well, so from that point of view you can eliminate a whole host of things.
"Beyond that, you've got to get as much data as you can and we'll work with Red Bull to find the right conclusion. There's a risk, of course, that we might never find it."
Hembery believes it unlikely that the deflation was caused by any debris lying in the gutter between the two parts of the Turn 1 exit kerb.
"We went and had a good look at the kerb with Seb and with the gutter," he added. "This is a wonderful circuit and there's nothing we've seen there that would cause you to be overly concerned.
"You've got to remember that 23 cars did the race going over the same areas and we didn't have any issues there, so that's unlikely. But he was the first car over that kerb, so if there was any debris there, he was the one that was going to get it."