French investigators said Monday that Formula One legend Michael Schumacher's ski accident in the French Alps was not due to safety breaches by the ski station or faulty material.

Schumacher has been lying in a coma in a French hospital since the December 29 accident when he crashed into a rock so hard that the impact cracked his helmet. He had been skiing with his son and a group of friends.

"There were no breaches by anybody. The accident occurred in an off-piste zone," in the posh ski resort of Meribel said prosecutor Patrick Quincy.

"The signals, markers and the information about the limits conformed to current French laws," Quincy said.

Schumacher was going at what has been described as normal speed for a "good skier" when he hit a rock, which caused him to crash into another boulder 10.4 metres (34 feet) away, prosecutors said. Both rocks were more than four metres from the marked trail.

The racing great has been in intensive care in Grenoble University Hospital since the accident.

After surgery to reduce bleeding and bruising he was placed in a medically induced coma and his body temperature lowered to reduce the risk of further damage.

Surgeons said he suffered bleeding and bruising on his brain and a scan showed "widespread lesions".

Schumacher's spokesman said on January 30 that the drugs used to keep him in a coma were being reduced with a view to bringing him back to consciousness.

His family said Thursday he was "still in a waking up process" which could take a long time.

Despite the decision by the investigators to close the case, Schumacher's family can still pursue legal action if they want.

German daily Bild said Friday that Schumacher had overcome a lung infection after reporting two days earlier that he had contracted pneumonia.

Schumacher dominated Formula One, winning the driver's championship, the biggest prize in motorsport, seven times and notching up 91 race victories.

As a driver, he was a daring overtaker with nerves of steel and an unrivalled feel for the sweet spot between risk-taking and recklessness.

That inevitably led to suggestions he could have been careless on the ski slopes. But it seems that he was just unlucky.

On the fateful day at Meribel he was reportedly skiing well within his capabilities. It is unclear why he went off-piste but when he did, he seems to have skied over a partially covered rock, which resulted in him losing his balance and hitting his head.