Michael Schumacher is fighting for his life in a hospital in France.
The seven time world champion, who retired from F1 for the second time last year, sustained a head injury while skiing off-piste at the Meribel ski resort on Sunday.
But the university hospital in Grenoble said in a statement: "He suffered a severe head injury with coma on arrival, which required immediate neurosurgical intervention. He remains in a critical situation."
Schumacher's manager Sabine Kehm confirmed the hospital's statement.
"His state of health has worsened and his condition is considered life-threatening, according to our information," the respected local newspaper Dauphine Libere reported.
The hospital has scheduled a press conference for Monday morning.
Citing hospital sources, French-language media claim Schumacher suffered a brain haemorrhage despite initially regaining consciousness after the fall.
"The fact that they undertook something almost immediately, that he was admitted to the surgical unit, suggests that something very serious has happened," Chris Chandler, a London neurosurgeon, is quoted by the Guardian.
Professor Gerard Saillant, a close friend of Schumacher's who treated his broken leg in 1999, rushed from Paris to assist with the treatment.
It is reported that Schumacher, who was skiing with his 14-year-old son Mick, is now surrounded by his family, while close friends Ross Brawn and Jean Todt are also at the hospital in Grenoble.
Former F1 driver Olivier Panis, a local, was reportedly turned away when he tried to visit Schumacher.
Tributes and well-wishes for Schumacher, a global sporting legend, have poured in, and his personal website has crashed under the demand for information.
"A security cordon has been placed around certain areas," a hospital spokesman was quoted by the Daily Mail. "Extra officers have been drafted in."