VITTEL, France (AP) - Denmark's Nicki Sorensen won the 12th stage of the Tour de France, with Lance Armstrong, Alberto Contador and overall leader Rinaldo Nocentini among those in the chasing pack.

Sorensen broke away Thursday and finished well ahead of Laurent Lefevre of France. Armstrong entered the day in third place overall. Contador, his rival and Astana teammate, was second.

Sorensen was part of a group of seven riders arriving several minutes in front of the main pack. The lead group was unchallenged during the 131-mile ride from Tonnerre to Vittel. The chasing pack was more than six minutes back.

Armstrong scrambled back to the main pack after the seven-time champion punctured a tire with about 37 miles left.

He pulled over to the side of the road while his team repaired a punctured back wheel. After a few moments, four teammates helped him catch up.

Armstrong is taking a cautious approach until the three-week race reaches the Alps on Sunday. He said the flat stages were nerve-racking.

"It is stressful with the crashes, on a stage like this where you have nothing to gain and then you lose everything because of a crash or a split in the group," the 37-year-old Texan said before the start. "You have to pay attention and try to avoid a crash."

Wednesday's stage was marred by several crashes and 19 riders were slightly injured.

"Yesterday, there was no way to avoid that crash, if you were just behind it, you were going down," Armstrong said. "So that is something which keeps you up at night. You have to constantly pay attention. I try to give myself a bit of space from people in front of me so I have a bit of time to brake."

Riders also learned that an earpiece ban scheduled for Friday's stage from Vittel to Colmar was overturned, allowing them to communicate by with team cars as usual. The ban was in place Tuesday and another was set for the 13th stage before the International Cycling Union reversed itself.

Many riders and team directors called the ban dangerous. Organizers hoped the experiment would inject drama into the race by having riders fend for themselves.