The motor racing world has been rocked by the death of Anthoine Hubert.
The 22-year-old Frenchman was killed following a high-speed accident during Saturday's Formula Two race at Spa-Francorchamps in Belgium.
Here, the PA news agency looks at some of the questions that have arisen following Hubert's death.
Hubert, who last year won the GP3 championship, hit the tyre wall at the top of Eau Rouge on the second lap of Saturday's F2 race. He rebounded back on to the track before American Juan Manuel Correa crashed into his car at 160mph. Hubert was taken to the track medical centre but died of his injuries one hour and 28 minutes after the crash. Correa suffered leg fractures and a spinal injury. On Monday, his family confirmed he will remain in intensive care at Liege hospital for a further 24 hours before he begins a period of lengthy rehabilitation.
Motor racing's governing body, the FIA, has opened an investigation into the accident. The inquiry is being led by Australian race director Michael Masi. The FIA will work alongside the Royal Automobile Club of Belgium. Masi refused to put on a date on when the investigation would be concluded.
Is Formula One safe?
Hubert's death was the first at a grand prix weekend in a quarter of a century after Ayrton Senna was killed at the 1994 San Marino Grand Prix. Frenchman Jules Bianchi died nine months after the injuries he sustained following a freak collision with a crane at the Japanese Grand Prix in 2014. Senna's death sparked radical safety improvements, including raised cockpits, the HANS helmet device, which protects the brain and neck, and most recently, the halo, which protects the driver's head. Tracks have also been modernised with wider, and bigger run-off areas, while spectators have been moved further away from the action.
How did the drivers react?
Daniel Ricciardo admitted that he contemplated withdrawing from Sunday's F1 race, while British teenager Lando Norris said he was left shaken by Saturday's tragedy. But Sir Jackie Stewart believes the tragedy may act as a wake-up call after accusing the drivers of taking too many risks in recent seasons. The drivers will discuss the accident with Masi on Friday in Monza ahead of this weekend's Italian Grand Prix. Monza, also known as the Cathedral of Speed, is the fastest track on the Formula One calendar.