After appealing for witnesses, the person has been identified, found, and is now in police custody in Landerneau, according to RTL. According to Reuters, she turned herself in.
The 30-year-old French woman is accused of involuntarily causing injury and faces a fine of 1,500 euros.
The incident occurred with around 45km remaining on stage 1's route from Brest to Landerneau, where the spectator in question was standing on the right-hand side of the road and holding a sign reading 'Allez Opi-Omi' (a German term of endearment for grandparents).
The spectator had her back to the peloton and the sign was sticking out into the road at handlebar height, causing Tony Martin (Jumbo-Visma) to collide with it, sparking a crash that rippled through the bunch and brought numerous riders to the ground.
Jasha Sütterlin (Team DSM) was taken to hospital with an injured hand, while Marc Soler (Movistar) finished the stage but abandoned the next morning after fractures in both arms were revealed. Eight other riders were seen by the race doctor and numerous more suffered minor injuries.
The race organisers then threatened to sue the culprit, with deputy director Pierre-Yves Thouault saying: "We are doing this so that the tiny minority of people who do this don't spoil the show for everyone."
On Monday, the police department of the Finistère region launched a judicial investigation and put out a call for witnesses in a Facebook post. Now they have found the person in question, charges can be levelled.
According to L'Equipe, a charge of involuntary injury caused by a lack of prudence would entail a fine of 1,500 Euros, provided the injuries sustained by those affected do not lead to more than three months of inability.
However, the consequences could be more serious if individual riders choose to take action. Soler has already hinted he could look to sue the spectator.
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