Pirelli denied any production or quality defects caused by high-speed blowouts by Formula One championship leader Max Verstappen and Lance Stroll at the Azerbaijan Grand Prix on Tuesday.
The company said in a statement that Verstappen's Red Bull and Stroll's Aston Martin teams adhered to Pirelli's set standards when tires were installed for the June 6 race in Baku.
This suggested that how the tires were driven had contributed to the incidents.
Pirelli said it also looked at other left-rear tires that had done the same or more laps as the damaged ones.
"This process established that there were no production or quality defects on any of the tyres, nor any signs of fatigue or contamination," the Italian company said.
It said the causes of the failures were clearly identified as "a circumferential breakdown on the inner sidewall, which may be related to the tread condition of the tyre."
This, it added, was "despite adhering to the prescribed starting parameters [minimum pressure and maximum blanket temperature]".
Pirelli said it and the governing FIA had agreed on a new set of protocols, including an advanced technical instruction distributed to teams, to monitor operating conditions during a race weekend.
The French Grand Prix in Le Castellet is set to take place later this week.
Red Bull said in a separate statement that they had worked closely with the FIA and Pirelli and that no defects were found in the car.
"We followed Pirelli's tire standards at all times and will continue to follow their guidance," the team leading the championship said.
Pirelli said after the race that he suspected the explosion may have been caused by external factors such as debris.
Verstappen and Stroll crashed in separate incidents when the rear-left tire blew straight on the same steep stretch.
Pirelli's F1 head Mario Isola then said: "No warnings or vibrations were detected and none of the other tires of the same age or older showed any signs of excessive wear. So we cannot exclude that the damage was done." It was caused by an external factor."