A Frenchman was photographed at a hostel in the Republic of Ireland in January by a Swiss couple on holiday. They became suspicious after noticing the similarity between the stranger and a photofit shown on television of a suspect seen near the dormitory in Brittany where Caroline was murdered nearly two years ago.
The French police have alerted the authorities in Ireland and circulated copies of the photograph, which features a man with dark eyebrows and long straggly hair. The man was photographed at Clifden, in the Connemara holiday region in the west of Ireland. Checks on hostels in the area are being carried out.
One of Caroline's teachers, Nick Ward, who is reported to have seen a strange man loitering near Caroline's bedroom on the night she died, 18 July 1996, has also seen the photograph and believes there are similarities between the two images.
The photograph could be an important lead in an investigation that has been hampered by a series of police blunders, including failure to follow up potentially vital clues.
Caroline was found raped and smothered in a youth hostel dormitory in the village of Pleine Fougeres, near Rennes. She was killed while four girl classmates slept in the same room.
John Dickinson, Caroline's father, said yesterday: "This could be an important development, but I'm not building my hopes up."
Captain Jean-Pierre Michel, the gendarme officer who recently took over the investigation, said: "They [the Swiss couple] were on holiday in Ireland taking pictures of crowds of people as they were sightseeing. When they were looking at their photographs they thought they had common characteristics with the image they had seen on the television.
"We are investigating this lead and trying to find out whether it is the same person."
He refused to give details of the photograph, saying it was too early in the investigation.