Fabian Cancellara retained the yellow jersey for a sixth straight day after the mostly flat 196.5-kilometre trek from Rouen to Saint-Quentin was almost tailor-made for sprinters except for a slight uphill near the end.
The Tour's doping demons returned to cast a shadow. A Dutch newspaper report said former teammates of Lance Armstrong — including five involved in the race — cut a deal with U.S. anti-doping officials for their testimony in a case against the seven-time Tour champion. As usual, the Tour riders tried to keep their focus on the race.
The barrelling pack overtook three breakaway riders with barely 100 metres left, and Greipel wheeled out in front a split-second ahead of Matt Goss of Australia, who was second, as Juan Jose Haedo of Argentina took third. Mark Cavendish was fifth.
Like in Greipel's sprint-finish victory a day before, a late crash tarnished the stage, and he counted himself "lucky" to avoid a spill two days in a row.
"Somehow I stayed on my bike," said Greipel, who turns 30 on July 16. "It was quite a tough finish there ... and it was also luck on our part to catch the breakaway."
The top standings didn't change: Bradley Wiggins, the leader of Cavendish's Team Sky, was second overall, seven seconds behind the Swiss leader. Defending champion Cadel Evans was 17 seconds off the pace in seventh.
Canada's Ryder Hesjedal was 35th in Thursday's stage, but sits eighth in the overall standings, 18 seconds behind Cancellara.
By holding the lead, Cancellara earned the right to wear the coveted yellow jersey for the 27th time in his career, a record for a rider who has never won the Tour.
"When you make history in this kind of way at the Tour, it's more special," said Cancellara, a time-trial specialist and the only man in yellow this year after winning Saturday's prologue.
As sprinters jockeyed for position with just over three kilometres left, Tyler Farrar of the United States tumbled in the middle of the pack. But his bike kept on going, and brought down at least two other riders including Peter Sagan of Slovakia, the winner of the first and third stages.
Farrar straggled across the line later alone, blood streaming down his right elbow and right knee. He then stormed into the bus of the Argos-Shimano team, looking for its sprinter Tom Veelers. Farrar angrily shouted, "You don't do that to someone!"
The stage start was overshadowed by a report in Dutch newspaper De Telegraaf saying five former teammates of Armstrong — all involved in this year's race — agreed to testify against him. Citing "well-informed sources," the newspaper said the U.S. Anti-Doping Agency has given six-month bans to the former Armstrong teammates Jonathan Vaughters, George Hincapie, Levi Leipheimer, David Zabriskie and Christian Vande Velde.
Vaughters, a team director at the Garmin-Sharp team, called the report "completely untrue." The four riders all declined to comment, though Hincapie said his thoughts were with Armstrong.
"I'm sad he is going through this," said Hincapie, the only rider to have been on all of Armstrong's Tour-winning teams. "He's done so many things for the sport. His accomplishments are incredible."
Cancellara said the case wasn't discussed in the pack.
"For cycling this is not good, that's for sure," he said. "That makes me sad. But on the other hand, we have to deal with that — and I hope it's not something that is going to take three or four years like ... in other cases.
"That is my biggest concern: that this is going to shut down fast."
The race got its first minor dose of rain on Thursday, and another dropout: Germany's Marcel Kittel, who has endured gastric troubles for the last few days, pulled out to reduce the field to 194 riders.
Friday's sixth stage — a 207.5-kilometre jaunt from Epernay in Champagne country to Metz — offers the last leg in the northern flats this week to favour sprinters, before a steep uphill finish on Saturday.
Eds: Associated Press writers Greg Keller and Samuel Petrequin contributed to this report.