Key events since Michael Schumacher's ski accident

Here are key events since an off-piste ski fall left German Formula One champion Michael Schumacher in a coma late last year.

French prosecutors on Monday closed a criminal investigation into the accident.

# December 29, 2013: Schumacher slams his head during a fall in a boulder-strewn section of the French Alpine ski resort of Meribel.

He is wearing a helmet but it is smashed into two pieces and he is evacuated by helicopter.

Doctors operate on Schumacher in Grenoble and place him in a coma, with a body temperature lowered to between 34-35 degrees C (93.2-95 F) owing to "serious brain trauma".

# December 30: Schumacher is in a "life threatening" condition and has a second operation to treat bleeding in the brain.

French authorities launch an investigation

# December 31: Schumacher's manager Sabine Kehm tells media the former race-car driver was skiing with friends and son Mick, and insists he was not going fast when the accident happened.

# January 1, 2014: A day before Schumacher turns 45, Kehm tells reporters that his condition is "stable".

# January 3: The French daily Le Dauphine Libere says police are checking a camera that was mounted on Schumacher's helmet.

# January 6: Doctors say Schumacher's state is critical but stable, a source close to the family speaks of a "slight improvement".

# January 8: Investigators rule out faulty skis, inadequate signage or excessive speed as possible causes of the fall.

# January 30: Doctors have started to reduce medications that keep Schumacher in a coma, but Kehm says it might be awhile before he is conscious.

# February 14: The German daily Bild says Schumacher has overcome a lung infection.

# February 17: French officials close a criminal investigation into the accident, concluding that it was not due to safety breaches.