PARIS — The Tour de France ended Sunday without a single rider testing positive for doping — so far.

PARIS — The Tour de France ended Sunday without a single rider testing positive for doping — so far.

At an event hit by at least one drug scandal every year since 2000, including six in 2008 alone, does the lack of positives mean the peloton is clean?

Cycling officials, race organizers and many competitors don't dare say so. Yet many hope the anti-doping fight — with a stiff new testing regime and screening techniques — is working.

"I'd say it's being won — I never said it has been won," said Pat McQuaid, who leads the International Cycling Union. "Even if we do end up with a positive in this year's Tour, it's not a disaster. The fact is that the culture is changing."

When the race ended, with Alberto Contador of Spain taking home his second yellow jersey and seven-time champion Lance Armstrong finishing third, the tests for doping did not.

"It's far too early to report on the testing, because we haven't received all the test results yet," said Pierre Bordry, leader of the French anti-doping agency.

France's anti-doping agency isn't even finished with last year's Tour.

The agency announced Sunday that it will retest blood samples from last year's Tour, mainly for CERA — an advanced form of banned endurance-boosting drug EPO.

The tests will concentrate on about 15 riders, who were told of the tests before the start of this year's Tour, Bordry said. He refused to identify the riders. The retesting will take place in September and October.

"We didn't want to do it during the Tour, because it could have disturbed the competition," Bordry said.

At last year's race, six competitors were caught by doping testers — four for using CERA. They included third-place finisher Bernhard Kohl and three other riders — Italian pair Leonardo Piepoli and Riccardo Ricco and Stefan Schumacher of Germany. Combined, they won five of the 21 stages.

Sport officials are bracing for the prospect that positive cases from this Tour could turn up days, weeks or even months from now.

Take Danilo di Luca, who finished second in the Giro d'Italia in May but didn't ride at the Tour. Cycling's governing body suspended him two months after the Giro ended for testing positive for the banned blood-booster CERA.

"Serenity at the Tour de France on this subject doesn't come easy," said race director Christian Prudhomme. "We're not going to imagine that all's the best in all possible worlds.

"There will no doubt be scandals tomorrow. As you saw, there was one in parallel with this Tour — the Di Luca case — though it didn't pollute this Tour."

Many riders applaud the new anti-doping efforts.

"It's been a breath of fresh air. I'm very happy. We've got to keep in the same direction," said David Millar of Britain, who served a two-year doping ban and has become an outspoken anti-doping crusader in the peloton.

"It's a cultural shift. It's great to see it actually paying dividends."