Though he is "making progress," the recovery period for injured Formula One racer Michael Schumacher is still unknown, his manager admitted.

Sabine Kehm said that Schumacher will have to undergo a "long and difficult" rehabilitation period for him to fully recover from his serious injuries.

According to Mirror, Kehm has revealed that they still cannot determine the exact period when the racing champion will be able to complete his recovery after his ski accident in the French Alps.

It was supposed to be just a chill and happy holiday for the entire family and friends when the accident happened, Daily Mail recalled.

Schumacher was skiing with his son when he skied in an area restricted by the resort then hit a partially covered rock causing him to lose balance. When he fell, he hit his head on a rock that destroyed his entire helmet. The video footage of the accident was, however, preserved in the camera which was attached to his head gear.

Daily Mail said that the film captured the full horror of the accident and was then used by the police in investigating the accident. Two months after the accident, Prosecutor Patrick Quincy ruled that there was no criminal violations in the incident and that it was purely an accident which started when Schumacher left the designated ski trail of the resort.

The 45-year-old racer damaged his brain and had serious head injuries after the accident. Despite the lack of updates regarding his condition, Schumacher is believed by Mirror to be "paralysed, wheelchair-bound and unable to speak and is receiving therapy at his home in Gland, Switzerland."

Some medical experts have already said that it would take years for the racer to return to his normal self and that this remains to be the best-case scenario.

Kehm earlier said that Schumacher is already making progress but he still has a long way to go. She also extended the gratitude of the racer's family to all the people who are praying for his recovery.

"I can only say again that the family is very happy and touched by the sympathetic messages. I believe that positive energy does them good. We appreciate the condolences from around the world," she was quoted by Mirror as saying.

Kehm also told Daily Mail that the accident was a big blow to the racer's family and that they found it very hard to accept the condition of Schumacher and what will come next for him.

It was reported that Schumacher's wife, Corinna, has really been hands-on in taking care of the racer with reports revealing that she has remained on his bedside almost all day. In the coming days or months, the people would be eager to receive positive news in terms of the racer's recovery.

Watch a special video uploaded by Michael Schumacher Fans on YouTube: