The Welshman suffered a suspected broken collarbone in a crash on the damp descent of the Col de la Biche, the first of three hors categorie climbs on a day expected to shake up the battle for the yellow jersey.

It was a fourth crash of the race for Thomas, who spent four days in the yellow jersey after winning the opening time trial in Dusseldorf last weekend.

After several days of blazing heat on the Tour, rain came on Sunday to make the descents of this mountainous 181.5km stage treacherous, with Thomas one of several riders to fall in the early going.

Three riders from the day's break - Movistar's Jesus Herrada plus Alexey Lutsenko and Bakhtiyar Kozhatayev of Astana - had crashed on the same corner as Thomas minutes before the peloton arrived.

Two-time Tour winner Alberto Contador also hit the deck as he fell on the ascent of the Grand Colombier, but the Spaniard was quickly back on his way with a push from spectators.