So, soon after Cancellara crossed the finish line Saturday, officials grabbed his bike, took it to a nearby tent and X-rayed it, checking to see if there was a tiny motor inside. His was one of 14 bikes X-rayed Saturday. All passed the inspection.

Image The Swiss rider and time-trial specialist Fabian Cancellara, above on the Erasmus Bridge in Rotterdam, finished 22 seconds ahead of Lance Armstrong. Credit... Lionel Bonaventure/Agence France-Presse — Getty Images

Cancellara, of the Saxo Bank team, called the need for the X-ray “ridiculous,” saying the accusations against him were false. Before the race, Pat McQuaid, the cycling union’s president, explained the need for the inspection.

“I honestly don’t believe that there has ever been a motorized bike in the peloton because the technology is not there yet to do it secretly,” McQuaid said, adding that a motor’s battery would not fit inside a bike’s frame. “But in cycling, if the suspicions are there, we’ve learned that we have to deal with those suspicions. These, like the others, are just another cloud over the sport that has dampened the sport. We’re doing all we can to get rid of those clouds.”

Fittingly, the prologue began in rain, under a gray sky. Tony Martin, a German rider for HTC-Columbia, rode early, setting the standard of 10 minutes 10 seconds. He ended up second. David Millar, a British rider for Garmin-Transitions, finished third, at 10:20.

Lance Armstrong, who at 38 says he is racing in his final Tour de France, took to the course near the end of the day. He finished fourth, 22 seconds behind Cancellara  but 5 seconds ahead of his rival Alberto Contador, who was sixth.