The bus was released after several hours and authorities refused to say what they were searching for. However, a police unit that specializes in doping investigations was involved in the search, according to the Associated Press.

“It was a routine control,” Quick Step spokesman Alessandro Tegner told AFP. “Maybe next week it's another team. Everything is all right.”

Members of the Quick Step team include Sylvain Chavanel, the French champion, and Tom Boonen, a sprinter from Belgium.

The French have vowed to be more vigilant with the race beginning Saturday with a 119-mile Passage du Gois stage. There may be more North American cyclists than ever in — call it a Lance bump — but Alberto Contador remains the favorite.

The attention he drew after testing positive for traces of clenbuterol shortly after winning his third Tour de France last year is a big reason for the increased attention by anti-doping authorities. So, too, is the continuing investigation swirling about seven-time champion Lance Armstrong, who has retired from the sport. Contador blamed his test result on bad meat and has appealed the result.