Prosecutors say that Schumacher was 'inanimate' nine metres from the piste in the French Alps, and that they have been unable to determine his speed at the time of the accident.
Prosecutor Patrick Quincy said Schumacher was skiing at 2,700 metres, on a small off-piste section of the Meribel ski resort, between a red and blue piste.
"Schumacher is obviously a very good skiier," Quincy told reporters. "At one point his skis in fact touch a rock, he loses balance, and he falls forward and his head hits a rock which is three metres 50 [centimetres] below."
He said the rock Schumacher hit was eight metres from the piste, and that the seven-time champion was "inanimate" nine metres from the piste.
The investigators said they were not yet able to determine the 45-year-old's speed at the time of the accident, but that he was trying to reduce his speed.
"It's difficult for me to evaluate the speed. The people involved in the enquiry are probably best to tell us how we can calculate the speed.
"Mr Schumacher is a very good skier. He was going on the left-hand side. He was on terrain that was more sloped.
"Because of that slope, he tried to reduce his speed, but there were few curves. We can't estimate his speed at kmph."
They added that speed "is not an important element of the investigation".
In a press conference in the Alpine town of Albertville, Quincy said that the press conference had been called to stop the spread of "false information" regarding Schumacher's accident, as his family are keen to stop rumours spreading.
French police added that they have been able to use a film from the helmet camera Schumacher was wearing to make a reconstruction of the crash, and have interviewed many witnesses and experts.
"We have examined the film in the camera fixed to the helmet of Mr Schumacher. We have yet to transcribe the film image by image to establish the place of the fall, the distance from the piste and the speed," Quincy said.
Up to 50 investigations like this one are carried out every season, the investigators said, adding that Schumacher's helmet and skis are being studied.
Quincy added he was "dubious" about reports regarding a film captured by a nearby tourist and that he had not seen it.
There had been some speculation that the signs around where Schumacher was skiing may have contributed to the accident, but Quincy said that they signs were "in accordance with the regulations". Investigators also said Schumacher's skis did not cause his life-threatening fall.
Michael Schumacher’s accident in the French Alps on December 29 left the former Formula One champion in a medically induced coma.
On Tuesday Schumacher’s wife appealed to the media to leave the hospital where her husband remains in a "critical but stable" condition, after having two operations to remove blood clots and reduce swelling.
In a statement, Corinna Schumacher said: “Please support us in our common fight with Michael.
“It is important to me that you leave the doctors and the hospital so that they can work in peace.
“I ask you to trust their statements and leave the clinic. Please leave our family in peace.”
There has been fevered media scrutiny of Schumacher’s condition, with one journalist even disguising himself as a priest in a bid to gain access to the 45-year-old’s hospital room.
The former racer’s manager, Sabine Kehm, said earlier this week that any further treatment will be kept private, amid conflicting reports and speculation about Schumacher’s condition.
"We would like to clearly stress that any information regarding Michael's health not coming from the doctors treating him or from his management must be treated as invalid and pure speculation," Kehm said.
Schumacher won 91 race victories during his 19-year career, and seven world championships. He won titles with Benetton in 1994 and 1995, before winning five straight championships with Ferrari from 2000.
The German retired in 2006, before returning in 2010 for three seasons with Mercedes, finishing on the podium once.