Pirelli chief Paul Hembery '100%' sure debris caused cuts to tyres in Belgian GP practice

Pirelli will closely inspect the Spa-Francorchamps circuit on Friday night after Sebastian Vettel and Fernando Alonso both suffered punctures during Friday's second practice session - but the tyremaker is "100 per cent" sure they were caused by debris.

He added: "Either way - whether it is fatigue of the tyre or something out there on the circuit - it is a worry and I hope they find debris on the track, but it hasn't affected other categories. There are GP3 cars on track at the moment and it hasn't been affecting them." With Hembery confident an external factor on the track was causing the problems, Pirelli will now conduct more detailed investigations into what exactly was cutting the tyres. "That's what we've got to find out now," Hembery said. "To be honest it's the sort of thing that you see throughout the weekend. We've seen a lot of signs on other tyres as well with some surface cuts, so there's clearly something, but I can't tell you what it is yet." Asked if something on the 7.004km track was damaging the tyres, such as a kerb, Hembery replied: "To be honest it could be anything. In the case of Alonso, you've got two holes through the top [of the tyre] - what on earth can cause that? "You've got to go and find it and that's obviously what we want to do." He acknowledged the incidents were a concern but said Pirelli would do all they could to get to the bottom of the issue before Saturday's Practice Three session. "It's a worry for the sport because we've got to go and find out what it is. It's not a lot we can do. We can try our very best to identify it and give indications of what could be causing it," Hembery added.