Mark Cavendish's Tour de France could be over after he was taken to hospital with his right arm in a sling having crashed in a chaotic finish to stage four, which was won by Frenchman Arnaud Demare.

Dimension Data's Cavendish fell heavily after taking a nudge from world champion Peter Sagan in the final 100 metres in Vittel, and indicated his Tour may be finished.

"Injury-wise I'm going to go and get it checked out. I definitely need stitches in this finger, it's bleeding a lot," he said.

"And the shoulder, there's something to do with that previous shoulder that I did in Harrogate - it's just sat backwards. I don't know if I've snapped the fake ligament in it or what - I'm going to go and get it looked at.

"I'm not a doctor, I don't know what, but I'm not optimistic anyway."

Cavendish, who has a property in Ongar, crashed out of the 2014 Tour de France in Harrogate when he suffered a separated right shoulder.

Here, the Manxman fell in the second of two late crashes on the stage from Mondorf-les-Bains, with the other sending race leader Geraint Thomas of Team Sky to the ground in the yellow jersey.

However, the Welshman was quickly up and on his way, with the maillot jeune safe as times were neutralised with both crashes inside the final three kilometres.

The news looked much worse for Cavendish, who was pushed into the barriers and was attended to by medics before slowly crossing the line, only holding on to his bike with one hand.

The 32-year-old had been forced into the barriers by Bora-Hansgrohe's Sagan, and the stricken Manxman brought down UAE Team Emirates' Ben Swift and Trek-Segafredo's John Degenkolb - the latter trying to bunny hop over Cavendish to avoid a direct collision.

"I was just following Demare, and Sagan came over," Cavendish added on ITV4. "I get on with Peter well, but I don't get the elbow - I'm not a fan of him putting his elbow in me like that.

"A crash is a crash, I'd just like to know about the elbow really."

Cavendish, a 30-time Tour stage winner, had recovered from a long bout of illness to make it to the Tour this year as he sought to close in on Eddy Merckx's all-time record of 34 Tour stage wins.

Sagan visited the Dimension Data bus after the finish to check on Cavendish.

"Mark was coming pretty fast from the back," the Slovakian said. "I tried but didn't have time to react to go left. He came to me and I had to defend."

Asked if he had apologised for the crash, he added: "For sure, because it's not nice to crash like that."

With time bonuses Sagan's second place is enough to push him up to second in the general classification ahead of Chris Froome, although there was speculation that he could face punishment for his role in the crash.

Thomas leads by seven seconds from Sagan, with Froome staying 12 seconds down. Froome was held up by Thomas' crash but did not go down.

"I'm okay," Thomas said. "The crash happened right in front of me. I tried to take off quite a lot of speed, but there was nowhere to go."

It was a first Tour stage win for FDJ's Demare, with Katusha-Alpecin's Alexander Kristoff third, Lotto-Soudal's Andre Greipel fourth, and local boy Nacer Bouhanni of Cofidis down in fifth.

It was a chaotic end to what had been a sedate stage from Mondorf-les-Bains in Luxembourg.

The day was a long and lonely one for Wanty-Groupe Gobert's Guillaume van Keirsbulck, who attacked from the gun and found himself in a sole breakaway for 191 kilometres of the 207.5.

Team Sky massed on the front of the peloton early on but had no interest in chasing down the Belgian, allowing him to build up a lead of more than 13 minutes.

He enjoyed plenty of television time for his sponsors before finally being swallowed up on the approach to Vittel, where the race exploded into life.