Formula 1 officials believe they have found the cause of the tyre failures at the Belgian Grand Prix on Friday that had caused the drivers concern.
There have already been a series of tyre problems this season.
Ferrari development driver Pedro De La Rosa, the chairman of the Grand Prix Drivers’ Association, said he was “very happy” that Pirelli and governing body the FIA had found what appeared to be the reason for the failures.
“We only asked to know what it was,” he told BBC Sport. “If it had been the first time we’d seen it we would have been relaxed, but after all the problems this year we were definitely concerned.”
Pirelli changed the design of the tyres following a series of failures during the British Grand Prix.
The new tyres are of a more robust construction and were designed with the extreme demands of Belgium’s Spa-Francorchamps track in mind.
Over a controversial few days following the British race, the grand prix drivers’ association threatened to boycott the subsequent German Grand Prix if there were any further problems.
The failures on Vettel’s and Alonso’s cars happened in the same area of the track, between Turns 13 and 14, the Fagnes and Stavelot corners.
Pirelli motorsport director Paul Hembery and FIA race director Charlie Whiting went out on to the track on Friday to investigate what might have happened after Hembery said initial indications were the tyres had been punctured by some debris.
They found a piece of tungsten – now understood to have come from Raikkonen’s car – in the kerbs on the exit of the Fagnes left-hander, otherwise known as Turn 13.
The right rear tyre of the cars would run over this kerb as they exited that corner, which immediately precedes the Stavelot and Paul Frere corners where the failures on the cars of Alonso and Vettel were discovered.
The piece of metal was exactly the same size as the hole in Alonso’s tyre and a similar diameter to the width of the cut running along Vettel’s tyre.