Alberto Contador with suspected broken collar bone after high-speed pile-up

Alberto Contador's Giro D'Italia hopes suffered a blow when the overall leader was involved in a high-speed pile-up at the end of the 183-km sixth stage on Thursday.

The Spaniard hit the deck during a mass sprint to the finish in the Tuscan town of Castiglione Della Pescaia but remounted his bike to roll over the line in the same time as stage winner Andre Greipel.

He still leads by two seconds in the general classification but struggled to pull on the Maglia Rosa at the presentation.

Tinkoff-Saxo team officials said Contador had hurt his knee and his shoulder and would undergo X-rays but they were confident he would be able to ride in Friday’s 264km seventh stage, the longest in this year’s race.

"Alberto is almost good, he had a very heavy fall towards the end. He's hurt himself on the knee and he's got a bad shoulder as you can see but I think he should be ok," Tinkoff-Saxo spokesman Jacinto Vidarte told Eurosport.

“Alright he’s hurt his knee but I think that he should be ok to continue.”

Italy's Daniele Colli (Nippo-Vini Fantini) will not be continuing after his team confirmed he had broken his arm in the crash which took down a sizeable chunk of the peloton as it roared towards the finish line.

Earlier on a relatively flat stage featuring just one categorised climb a five-man break was caught with 14km remaining with Contador’s team and the Astana outfit doing most of the work on the front.

Greg Henderson positioned team mate Greipel perfectly on the front with 200m to go and the German veteran did the rest, pumping hard to the line to maintain his record of winning at least one stage in every Giro has he ridden.

Contador's main rivals for victory all came through unscathed with Astana's Fabio Aru and Team Sky's Richie Porte avoiding any mishaps to stay in the hunt.