LAVAL, France, June 30 (Reuters) - The spectator who caused a massive pile-up during the first stage of the Tour de France has been arrested after presenting herself at a police station, a source close to the investigation told Reuters on Saturday. The spectator, a 30-year-old French woman, is in custodyat a police station in Landerneau, Brittany, the northwest French region where the Tour de France, the world"s biggest cycling event, held its first four stages. The spectator is accused of involuntarily causing injury and putting the life of others at risk. On Saturday, German cyclist Tony Martin was sent tumbling when he rode straight into a cardboard sign being held out by a fan looking the other way at a television camera, creating chaos with 47 kilometres left of the stage. Another huge pile-up occurred in a nervy finale on narrow roads on Monday, leading the Tour de France riders to put their collective foot down one kilometre into the fourth stage on Tuesday - literally - bringing the race to a halt for about a minute in a silent protest for safer racing conditions after the crashes. read more Wednesday"s fifth stage is a 27.2-km individual time trial from Change to Laval, and all eyes will be on the overall contenders.