Marie-Jeanne Meyer was in the middle of sitting her Baccalauréat exams and was due to sit her French exam on Monday morning.
The girl left her home in the small town of Tournon-sur-Rhône at 6pm on Saturday evening for her usual run of 30 minutes. When she didn't return the police were alerted and a search started later that evening.
AFP reported that the search was stepped up on Sunday with 200 police officers using dogs and a helicopter. Searching continued through the night but there has still been no sign.
Marie-Jeanne lives with her parents and younger brother and sister. According to Frédéric Sausset, mayor of the small town, she is "top of her class".
Heavy rain on Friday made some parts of her usual route dangerous but Sausset thought it was "unlikely she had injured herself in a fall as the helicopter has thoroughly combed the area."
The search started again on Monday morning.