Pirelli's Paul Hembery claims both tyre failures on Friday were due to debris on the circuit.
Aug.24 (GMM) Formula One drivers are threatening to 'boycott' the Belgian Grand Prix if their concerns about tyre safety are not eased, according to Italy's La Gazzetta dello Sport.
The new saga has arisen after Sebastian Vettel suffered a rear failure during practice at high-speed Spa-Francorchamps on Friday, reviving fears of a repeat of June's tyre-exploding British Grand Prix.
It later emerged that a similar failure had occurred at the rear and on the same side on Fernando Alonso's Ferrari, while Speed Week said yet more drivers had also reported problems.
Pirelli's Paul Hembery reacted by insisting the problem is "very different" to what was seen at Silverstone, according to SID news agency.
"From initial analysis it appears that both (Vettel and Alonso's failures) were caused by an outside factor, probably debris on the track," the Briton was quoted in an official statement.
Formula One veteran Mark Webber, however, does not believe it.
"We need answers and debris is not the answer," he is quoted by the Daily Mail.
Reports, including in the Guardian newspaper, said the drivers have asked F1 race director Charlie Whiting to "seek a guarantee" from Pirelli about the safety of the tyres.
That would require the Italian company to give definite answers about precisely what debris cut the tyres on Friday.
"It is a worry for the sport," Hembery said, "because we have to go out and find what it is."
The implication is that Pirelli might not be able to come up with a definite answer, risking the prospect of drivers going through with their threat.
So Hembery showed journalists photographs of the damaged tyres, arguing that all the evidence points to debris having caused the cuts.
"There's not a lot we can do about that," he is quoted by The National.
"We have seen a lot of signs on other tyres, small surface cuts, so there is clearly something. I cannot tell you what it is, but it is from external sources," added Hembery.