POLICE have been asked to launch an investigation after around 30 Tour de France riders suffered punctures when tacks were placed on the route.

Race officials called for the French authorities to look into the apparent sabotage at stage 14 of the race between Limoux and Foix.

Following the punctures, race leader Bradley Wiggins temporarily called a halt to competitive racing after defending champion Cadel Evans was among those affected.

Wiggins, who still leads by more than two minutes, slowed the pace to allow Evans to return to the group.

Race director Jean-Francois Pescheux said it would be difficult to find the culprit as thousands of people had lined the roadside during the climb.

He added: "The nails were mainly thrown on the ground around 200m from the summit."

Mr Pescheux also praised Wiggins, lead rider for team Sky, for demonstrating fair play.

He said: "Bradley did the right thing in sitting up and he will have made a lot of friends by doing that."

Wiggins, who is aiming to become the first British rider to win the race, said calling a truce was the honourable thing to do, adding: "Nobody wants to benefit from someone else's misfortune."

The cyclist claimed the incident showed just how vulnerable riders are in the competition.

He said: "There's nothing stopping more of that sort of stuff happening. It's sad. These are the type of things we have to put up with as cyclists. I think people take that for granted sometimes, just how close they can get to us. If that happened in a football stadium, or wherever, you'd be arrested, CCTV.

"But we're out there, quite vulnerable at times, very close to the public on climbs."

Wiggins and the other three riders in contention to win the race all reached the summit together. Spain's Luis-Leon Sanchez, who was involved in a breakaway, won the stage.