Rome, July 5 - Pirelli said Friday it was unruffled at Ferrari driver Fernando Alonso's threat to snub a test of its Formula One tyres later this month, as the furore over a series of blow-outs at last weekend's British Grand Prix continues. Pirelli has said its tyres are safe and that a probe showed the explosions were down to a combination of factors, including teams using rear tyres intended for the right rear on the left side of their cars and running them at lower pressures than recommended. Nevertheless, the company has taken modified rear tyres to this weekend's German Grand Prix. The Grand Prix Drivers' Association on Thursday threatened to stop racing if there were any more tyre explosions. Alonso, meanwhile, said he was reluctant to take part in tyre tests at the Silverstone track, the same circuit the blow-outs occurred at. "(World champion) Sebastian Vettel and the other drivers are coming," Pirelli Motorsport Director Paul Hembery said when asked about the possibility Alonso will not take part in the test. "I'm sorry for him".