Hospital officials say Felipe Massa is in "life-threatening" condition after undergoing emergency surgery on a skull fracture following a violent crash in Hungarian Grand Prix qualifying on Saturday.
Officials at AEK military hospital said Massa will be kept sedated on a respirator overnight in the intensive care unit.
Medical director Peter Bazso said at a news conference that "Massa's condition is serious, life-threatening but stable." Bazso and chief surgeon Lajos Zsiros said they expect the Brazilian driver to be awoken on Sunday.
Ferrari denied Massa's condition was life-threatening, with team spokesman Luca Colajanni saying his state "was a positive one."
Massa underwent surgery one hour after arriving at AEK hospital at 3:20 p.m. local time, the doctors said.
The 28-year-old Massa also suffered a concussion, but was conscious and in stable condition when he was airlifted to the hospital, Ferrari said.
A spring that had fallen off Rubens Barrichello's Formula One car flew up and struck Massa in the helmet during qualifying. An apparently dazed Massa continued straight through a curb, across the track and through the gravel area alongside the circuit before slamming into the tire barrier.
The impact of the rear suspension part — a standard component which Brawn GP team principal Ross Brawn believed was made of steel — damaged the left side of Massa's helmet, ripping out the visor and leaving a long dent on its side. Blood was seen above Massa's left brow.
"Following a complete medical examination it emerged that he had suffered a cut on his forehead, a bone damage of his skull and a brain concussion," Ferrari said in a statement.
Barrichello, a fellow Brazilian, went to the medical center to check on Massa's condition and said the Ferrari driver appeared to be doing fine despite the cut above his left eye.
"He was in shock," Barrichello told The Associated Press. "Considering the gravity of the accident, I think he's in OK shape."
Massa appeared to regain consciousness just before the crash at turn No. 4 as his front brakes seemed to lock ahead of the violent impact.
He remained in the car for a considerable time and was assisted out before being taken to the medical center. He was then taken to the helicopter on a stretcher, wearing a neckbrace.
The crash shredded the front of his Ferrari, with both tires gone and the front nose open.
The crash came less than a week after Henry Surtees, the son of former F1 champion John Surtees, died in an F2 race last Sunday. Surtees was struck in the head by a tire from another car, causing him to lose consciousness and drive into a barrier.
"It is not a coincidence that something happened right now," Barrichello told reporters. "Something needs to be done. Yes, absolutely."
No F1 driver has died on the track since three-time champion Ayrton Senna's crash at Imola 15 years ago.
The accident was also reminiscent of Heikki Kovalainen's high-speed crash at last year's Spanish GP, when the McLaren driver slammed into a wall at high speed. Kovalainen spent the night in a hospital with a concussion.
"What happened to me in Barcelona was a very nasty accident. But I think it was a pretty freak accident and I don't know how to prevent that," Kovalainen said. "It was very unfortunate. But I think we should discuss it."
Surtees' death led drivers to discuss the issue of debris and head safety at length during their usual pre-race meeting on Friday.
Renault's Fernando Alonso took pole position for Sunday's race after qualifying was delayed for nearly 30 minutes because of Massa's accident.