Toro Rosso is still unsure about the cause of the punctures Daniil Kvyat suffered during Abu Dhabi Grand Prix practice on Friday.
The Russian driver missed most of the running in FP1 after his left rear tyre exploded because of a rim issue, and was again forced to stop in the afternoon after suffering the same problem.
As a precaution, the team decided to also stop teammate Carlos Sainz, the Toro Rosso duo managing just nine laps between them and ending up at the bottom of the timesheets.
It is not the first time Toro Rosso has suffered punctures, having been in the same situation a few times in the last few races.
Team boss Franz Tost admitted the team was still seeking answers.
"After facing two failures on the rear rim of Daniil's car today, it was decided to avoid sending Carlos out on track again because we still haven't understood 100 percent where the problem is coming from," said Tost.
"We will now work hard tonight, together with the engineers back in Faenza, and hopefully we will sort it out for tomorrow."
Sainz, who suffered the same problem during the US Grand Prix, admitted the team had not found the cause back then.
"We put solutions in place that apparently cured the problem," he said. "It happened also in Brazil. Hopefully it happens here, but the real cause we don't know it yet.
"First we need to find the cause and at the moment we haven't found it. We are putting solutions but without finding the cause of the puncture.
"If tonight they tell me they know why we were having these punctures I will be fully confident. But we haven't found the cause."
Pirelli technical boss Mario Isola ruled out debris had caused the punctures.
"It is not related to the tyre, absolutely," he said. "It's the team that will analyse the information on that but the tyres were OK, both. It is not the tyre."