Last November French police released a photofit of an unshaven "caveman" with long, dark, straight hair and dark eyebrows, the main suspect in the July 1996 murder at a hostel at Pleine Fougeres, Brittany.
French sources now say that two days before Caroline, 13, was killed, during a trip with Launceston Community College, Cornwall, a man resembling the suspect asked the way to Pleine Fougeres. At the time he was in Antrain, only 10 miles away, and was described as looking like a drifter, rough, unshaven, with unkempt hair.
French police say a man of similar description fled the Pleine Fougeres hostel after being surprised by a teacher and a girl when he tried to enter a dormitory other than the one where Caroline was sleeping.
It is understood the French police believe he drove to another youth hostel at St Lunaire, 25 miles away, and attempted to suffocate a 14-year-old Manchester girl with a cotton wool wad. But when she screamed he fled, and is thought to have driven back to Pleine Fougeres where he suffocated Caroline using the same cotton wool wad.
The latest development comes four days before the third anniversary of Caroline's murder.
Caroline's father John Dickinson, 42, from Bodmin, will travel to France later this week to make another appeal for information about the killing, and meet the murder hunt team.
He said this week it was still not too late to catch her killer, who left a DNA trace at the scene.
Mr Dickinson said: "The leads are still coming in. I am still convinced he will be caught. Somebody does hold the clue, whether it is in the vicinity of Pleine Fougeres or elsewhere in France."
Earlier this year Mr Dickinson was in France to call for the establishment of a Europe-wide DNA database to help catch serious criminals.
Mr Dickinson said the search for Caroline's killer had been "beyond a nightmare".