Nico Hulkenberg strengthened Porsche's lead in his first Le Mans 24 Hours race on Sunday while champions Audi ran into trouble when their quickest car shed bodywork with seven hours remaining. The Force India Formula One driver, in the number 19 Porsche, led the number nine Audi by just over two minutes at the 17 hour mark with the safety cars deployed for a fourth time. Hulkenberg, who shares the car with Briton Nick Tandy and New Zealand's Earl Bamber, had arrived in Le Mans straight from the Canadian Grand Prix and will be heading to Austria after the weekend.There had been little to separate the two German manufacturers, both part of the Volkswagen stable, as dawn rose over the Sarthe circuit. However, Marcel Fassler had to pit the number seven Audi shortly before 0700 local after a large part of bodywork flew off the car without warning. That cost seven minutes for repairs and pushed the Swiss, who is chasing a fourth win with team mates Benoit Treluyer and Andre Lotterer, down to fifth. Australian Mark Webber, the former Red Bull Formula One driver, was third in the number 17 Porsche he shares with New Zealander Brendon Hartley and Germany's Timo Bernhard after leading at the quarter distance. Audi are chasing a 14th win in 16 years with their diesel hybrid car but face a tough battle from 16 times winners Porsche, who returned with a full factory effort last year. Porsche last won the race in 1998.