Saturday’s final practice for the Russian Grand Prix was cancelled following a heavy smash.
Spaniard Carlos Sainz ploughed into barriers, bringing a halt to the morning session.
Television images showed the 21-year-old rookie driver strapped to a stretcher, giving a thumbs-up sign after being extracted from the wrecked Toro Rosso car.
He was airlifted from the circuit to a local hospital in a helicopter, though initial reports are positive.
"Carlos is conscious, he's with the doctors now. They will see if he can continue the race weekend," team principal Franz Tost said.
Television replays showed the car snapping left and hitting a concrete wall, then skidding along at speed in a cloud of debris before slamming into the TECPRO impact-absorbing barriers at Turn 13.
The nose of the car, with the front left wheel dangling on tethers in front of the driver, was then buried deep into the barriers.
"Is he OK? Because it looks like a big one," Sainz's team mate Max Verstappen over the team radio as the medical car attended the scene of the impact and the paddock collectively held its breath.
"We lost the power on the car, we don't know," came the initial reply.
In an indication of the severity of the accident, race officials said the session - which was halted with 25 minutes remaining and the clock still counting down - would not be restarted.
Drivers have had little time to set their cars up for the track after Friday's two sessions were hit by a morning diesel spillage and afternoon bad weather.
Germany's Nico Rosberg was quickest for Mercedes in the half hour of running on Saturday.
His was the best time of 1:38.561 seconds on the circuit that winds around some of the landmark venues used at the 2014 Winter Olympics.
World champion and series leader Lewis Hamilton, who will be aiming for his 12th pole in 15 races, was third fastest for Mercedes.
The German manufacturer's engines powered the top six on the time-sheets, with Valtteri Bottas second for Williams and Force India's Sergio Perez and Nico Hulkenberg fourth and sixth while Brazilian Felipe Massa was fifth for Williams.
