Canadian driver Robert Wickens has reportedly suffered broken legs, a broken right arm, a spinal injury and a bruised lung following a terrifying crash in the IndyCar race at the high-speed Pocono Raceway in Pennsylvania.
Surgery is also anticipated once the injuries are confirmed.
IndyCar said Wickens also suffered a pulmonary contusion. "He's hurt. He's awake and alert, and at least he's alive", said driver Sebastien Bourdais.
But animosity between IndyCar drivers tends to dissolve quickly amid grim reminders of the sport's dangers.
Wickens was "awake and alert", but has been taken to a local hospital for further evaluation.
Alexander Rossi secured the IndyCar Series victory. Wickens' vehicle climbed and went up into the fence and spun several times in mid-air before coming to rest against the inside retaining wall.
Australian Will Power and New Zealander Scott Dixon both avoided the carnage and returned to finish in second and third place respectively when the race resumed almost two hours later.More news: Former Indian Prime Minister Atal Bihari Vajpayee Dies
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The contact caused Hunter-Reay's vehicle to careen into the wall and Wickens' auto was pulled along for the ride.
The accident caused a delay of almost two hours while the fencing was fixed, with about 25 metres needing to be replaced.
Alexander Rossi was as anxious as the rest of the IndyCar field when a violent wreck shot Robert Wickens' auto airborne, ripped up the catchfence and left the tub of the rookie's Honda toppled on the asphalt.
Robert Wickens went soaring into the fence at Pocono Raceway in a scary wreck that brought the IndyCar race to a halt. IndyCar driver Justin Wilson was killed at Pocono in 2015 when he was struck in the head by debris from a auto that crashed ahead of him.
Other drivers involved in the ensuing chain-reaction crash included Wickens's team-mate James Hinchcliffe - who spun to avoid him but was struck hard by the Dale Coyne Racing Dallara-Honda of Pietro Fittipaldi. Hinchcliffe seemed to be in pain, grabbing his wrists as he slowly left his vehicle. The caution flag waved nearly immediately when Graham Rahal ran into the back of Spencer Pigot as they reached the front straight.
But Bourdais, who said the repairs were "pretty lousy", raised his concerns about the quality of the repairs and condition of the fence before he got back in the vehicle. Hinchcliffe headed to the hospital to be with Wickens, who is a close friend and Schmidt Peterson Motorsports teammate.
It was the second crash of the race, as Rahal wrecked Spencer Pigot while the green flag flew on Lap 1. Pigot hit an inside wall, and Rahal's auto went to the pits for repairs.
Scott Dixon pits during the IndyCar auto race at Pocono Raceway. Wickens has four consecutive top-five finishes, including second at Mid-Ohio and third at Toronto.