PERROS-GUIREC, FRANCE (AFP, REUTERS) - French police on Sunday (June 26) appealed for witnesses as they launched a probe into Saturday's giant pile-up at the Tour de France which was caused by a spectator.

The woman had held up a sign with 'Granny and Grandad' written in German, looking up the road towards the race's motorbike cameras with her back to the speeding peloton.

German rider Tony Martin brushed into her, lost his balance and fell, causing a sickening wave of falls that swept through most of the peloton, leaving them in a tangled mess of bikes and bodies.

"The major issue on the Tour is road security," Lieutenant-Colonel Joel Scherer of the French Gendarmerie told AFP on Sunday. Another policeman told AFP that "zero fatalities" was their bottom line assignment aim on a Tour de France or any bike race.

The woman, who was wearing a yellow raincoat, reeled away in horror when she realised the extent of her folly, but she then disappeared into the deep roadside crowds, her sign folded away beneath her arm.

DSM's German rider Jasha Sutterlin was the only cyclist who had to pull out immediately. Eight other riders needed treatment from the official doctor and a host of others were treated for grazes, bruises and cuts caused by the pile-up which took place with 47km to go.

Race organiser ASO has filed a lawsuit against the unidentified spectator.

"We are suing this woman who behaved so badly," Tour deputy director Pierre-Yves Thouault said. "We are doing this so that the tiny minority of people who do this do not spoil the show for everyone.

"We are going to repeat our calls for fans to behave time and again, through the police on the side of the road and our social network.

"Most of the fans are peaceful but I want to stress that you come see the Tour, you don't take selfies, you keep your kids close to you."

The police said that when they catch the culprit, they intend to charge her with "unintentional short-term injury through a manifestly deliberate breach of a duty of safety or care", Lt-Col Scherer said. He confirmed that no member of the public was injured.

The Tour started on Saturday from the Atlantic port of Brest.

Following the relaxation of French coronavirus restrictions, the public turned out in massive numbers along the narrow Brittany roads for a stage eventually won by Frenchman Julian Alaphilippe.

But their actions irked both riders and organisers.

"We witnessed inadmissible behaviour today (Saturday) with people running across the road in front of the race and children left to their own devices," race director Christian Prudhomme told French media. "You come here to see heroes. If you want to see yourself, look in the mirror."

Israel-Start Up Nation sports manager Rik Verbrugghe said that while riders enjoyed the support of fans, they created an extra stress in the peloton.

"It's a good thing to have all those fans on the side of the road but it brings extra stress, extra danger," he told reporters. "We saw also the first crash was because of a fan. Most of the time the fans make it pretty dangerous because they make the road narrower. But it's part of the game, that's what makes cycling so exciting and so beautiful."

Martin urged the fans to be more respectful.

"This message is for the people who think that the Tour de France is a circus, for the people who risk everything for a selfie with a 50kph fast peloton... please respect the riders and the Tour de France," the German wrote on Instagram. "Use your head or stay home!"

On Sunday, four official race vehicles preceded the peloton, which set off minus three more riders who were hurt in a separate crash later on Saturday, warning over-excited roadside fans to keep their distance.

"We are telling people to keep off the route and to control their children," Scherer said.

Some 500 gendarmes were amongst the 14,000-strong security forces along the 183.5km route on Sunday.

Despite these efforts, the peloton had to slow down in sections due to massed ranks of spectators along Brittany's Cote d'Armour coast spilling onto the course and narrowing it significantly.

Earlier, youths had set off flares and fireworks by the roadside at the moment the riders were speeding past them.

The second stage was won by Mathieu van der Poel of the Netherlands. He attacked with 700 metres left in the final ascent to Mur de Bretagne to beat defending Tour champion Tadej Pogacar and his fellow Slovenian Primoz Roglic, who were second and third respectively, six seconds behind.