| SILVERSTONE, England
SILVERSTONE, England Formula One and tyre supplier Pirelli faced a full-on crisis on Sunday after the British Grand Prix came close to being stopped for safety reasons due to a spate of explosive high-speed blowouts.
The spectre of Indianapolis 2005, when only six Bridgestone-shod cars competed in a farce of a U.S. Grand Prix because all those equipped by tyre supplier Michelin could not compete safely, lurked in the background.
There were also uneasy flashbacks to the 2009 Hungarian Grand Prix, when Ferrari's Brazilian Felipe Massa suffered a near-fatal head injury after being struck by debris thrown up from a car in front.
With television images broadcast around the world showing bucking cars scraping along on rear left wheel rims stripped of rubber, the drivers wrestling to keep them on the road, the sport breathed a sigh of relief that the race had ended safely.
Race director Charlie Whiting told reporters that it had been a close call, however.
"It was quite close to being red flagged. It did occur to me to do that," he said, when asked how many more failures it would have taken before he had acted. "I don't want to put a figure on it but it was close.
"I don't think we've seen anything like this. I can't remember anything. To have four total catastrophic failures, I believe, is a first."
Britain's Lewis Hamilton, the 2008 world champion who had led for Mercedes from pole position, was the first casualty when his rear tyre blew after eight laps at around 200kph and shed debris behind him.
He was followed by Ferrari's Felipe Massa, Toro Rosso's Jean-Eric Vergne - who was going the fastest of all - and then McLaren's Sergio Perez. Sauber's Esteban Gutierrez had a front tyre failure.
Mercedes' race winner Nico Rosberg had signs of imminent delamination - when tread peels away from the rest of the tyre - when he made a pitstop and champions Red Bull said cuts were found on the tyres of triple champion Sebastian Vettel, who retired with a gearbox problem.
"The safety is the biggest issue," said Hamilton, his words echoed by others around the paddock in a sport that has not had a fatality on track since Ayrton Senna died at Imola in 1994. "It's just unacceptable.
"Someone could've crashed. I was thinking behind the safety car that it's only when someone gets hurt that something will be done about it."
With the next race in Germany only a week away, Pirelli's motorsport director Paul Hembery said the Italian company - which has come under fire all season for the performance of its product - was making the investigation a top priority.
"We can exclude that the new bonding process, which we introduced at this race, is a cause for the tyre failures we have seen today," he added.
"There might be some aspect to this circuit that impacts specifically on the latest version of our 2013 specification tyres but at this point we do not want to speculate."
McLaren team principal Martin Whitmarsh declined to use the word crisis but said safety was the main concern.
"We are lucky no one has been hurt," he told reporters. "For people like Checo (Perez) it has destroyed his weekend, but first and foremost we are primarily concerned about the safety of our drivers.
"I think there is an argument that Nuerburgring is a slightly less severe circuit than Silverstone, but we have Spa (Belgium) looming not long after that and we would certainly not want to go there with these tyres."
Whitmarsh said the sport could not wait for a scheduled meeting of the governing International Automobile Federation (FIA) working committee on Wednesday to discuss the situation.
"You just have to say to Pirelli 'Do whatever you can do by Germany'," he said. "They know what stock they have, they know what they can do practically before Germany and they should do whatever they can to enhance the safety and durability of the tyres."
Asked whether the German race might be cancelled, Whitmarsh suggested a solution would be to go back to last year's specification of tyres.
"In fairness to Pirelli, I don't know how they can respond in such short order but we have to do what we can to support them," he said.
"We don't want an Indianapolis but cancelling a race is a big step, we don't have all the technical insight Pirelli have," he continued. "All I would ask is they do everything they can to give us the most durable tyres they can for next weekend."
Red Bull principal Christian Horner agreed.
"The most logical thing would be to go back to the tyres that worked well for them previously," he told reporters. "The tyres they had last year did not have these failures.
"Whatever has changed, has changed but you would have thought the most logical thing would be to go back to the tyres that had served them well."
(Reporting by Alan Baldwin; Editing by Sonia Oxley)