Nico Rosberg has admitted that it is a "bit worrying" that there is no definitive answer as to what caused his tyre blowout during Belgian Grand Prix practice.
Although a structural integrity issue has been ruled out, investigations have not yet delivered a proper explanation of what caused his tyre to give out at 190mph in Friday practice.
The only potential avenues that have been looked at are that the tyre issue was caused by either track debris or a part of the car rubbing on the tyre when out on track.
When asked about the situation, Rosberg said: "The problem is that we don't really understand it. There are theories, but no real evidence, so that is a bit worrying for sure.
"We are keeping a close eye on it and have done some measures to make sure it doesn't happen again. So we have to hope it works out and doesn't come together."
Following overnight analysis of the right-rear tyre that failed on Rosberg's Mercedes on the 190mph approach to Blanchimont corner in second practice, Pirelli has been working hard to try to fully understand what caused the incident.
It has ruled out a structural integrity failure, and is also sceptical that the tyre failure was caused by kerb damage.
Speaking about the incident, Pirelli motorsport director Paul Hembery said that the manner of the tyre failure – with cord emerging on the Kemmel Straight – could only be explained through an external cut.
"Looking at the video footage was the clearest indication that to get that type of component of the tyre to start unwrapping, and the only way is to have a cut coming from the outside of the tyre.
"That cord you could see is in position to stop the tyre gaining in circumference so as it is speeding up, if that cord is no longer there, the tyre is increasing and decreasing in circumference and that creates an ultimate failure."
First time failure
Hembery said the nature of the failure – which manifested itself in the centre of the tyre – had never been seen before in F1.
"We have never seen that in Formula 1 before," he said. "So it is certainly a one off – there are a lot of people in the paddock and they have been around a long time.
"I think people are scratching their head as to when they had seen something like that, so it is a very rare type of failure."
Car part theory
One avenue that has been investigated is whether the failure – which appeared to have been triggered by only a minor piece of damage to the external surface of the tyre – was caused by a part of the car.
A theory that emerged was whether or not flexing at the rear of the car under either acceleration from a race start, or from the unique demands of the Spa circuit, meant a floor fin fitted in front of the rear tyre could have come in to contact with the tyre.
Mercedes has conducted a thorough investigation in to the matter to check on this, and is confident that there is no way its car parts were to blame.
Hembery said that there had been occasions in recent years where bodywork around the tyres had caused trouble, but was not sure if it was the case this time.
When asked if bodywork could have been a factor, Hembery said: "That can happen – we have had examples in our time in F1 of these sorts of things happening.
"But in this case, I don't believe so. I think Paddy Lowe ruled that out completely."
No debris sign
That leaves the most likely outcome debris – because any kerb damage would likely have been to a sidewall rather than the centre of the tyre.
"We did check the kerbs but we didn't see anything particularly untowards. You can never rule those things out," added Hembery.
"But the best example we can give you is that two years ago here we had a puncture, which we knew was a puncture. We saw a great big hole in the tyre.
"We were fortunate in that case, we found a skid block on the circuit that matched the hole so we were able to define that.
"But we are not always that lucky and not always that able to find the exact point of time on a seven-kilometre circuit where something like that may have occurred.
"So that is the unfortunate side. The positive aspect from our point of view is that we have not got any concerns about the integrity."