UPDATE -- Authorities announced Wednesday they have arrested the involved fan.
Authorities have launched an investigation after a woman standing with fans along the Tour de France route caused a disastrous crash involving several riders over the weekend.
The woman was holding a piece of cardboard with a message on it in the far west region of France where the first day’s racing was taking place Saturday. Media outlets show the woman stepped out in front of the pack of cyclists while she held up the sign, appearing to hold it for the cameras.
The Independent newspaper in the UK reports the message was to the woman’s grandparents.
The sign reportedly hit one of the riders near the front of the pack. The cyclist fell, leading to more crashes as riders behind him fell.
The crash was significant, taking down or slowing down dozens of riders. The race was held up for several minutes as bicycles and people were detangled.
The woman left the area before authorities could talk to her.
Investigators in the Finistère region of western France are calling for witnesses to help them find the fan. They are investigating the cause of "unintentional injuries....by manifestly deliberate violation of an obligation of safety or prudence.”
The organization that runs the Tour de France has made a formal complaint to authorities about the crash, according to CNN.
At this time, at least three riders have withdrawn from the race following Saturday’s crash.
A second, unrelated crash happened during Saturday’s first stage of the race. This one was just eight kilometers from the end.