Bourg-en-Bresse, France ? Lance Armstrong called the ongoing French doping probe into his U.S. Postal Service team “a joke,” but added that he doesn’t care about the investigation anymore.

Instead, Armstrong is focused on winning his fourth straight Tour de France and trying for a fifth next year.

Overall leader Lance Armstrong leaves the podium after finishing 24th in the 18th stage of the Tour de France on Wednesday. Armstrong has been dogged by doping allegations throughout the race.

Armstrong finished 24th in Friday’s 18th stage, 11 minutes, 42 seconds behind winner Thor Hushovd. The Texan maintained his 5:06 advantage over Spain’s Joseba Beloki in the overall standings with two stages remaining.

Armstrong has been heckled by fans shouting “Dop-AY! Dop-AY!” (“Doped! Doped!”), but French judicial officials recently said the probe into the U.S. Postal Service launched in the fall of 2000 has revealed no evidence of wrongdoing.

Armstrong said the investigation was “a joke from the beginning.”

“Immediately they (French judicial officials) knew the evidence was clean, but they kept the case open,” he said. “It’s not an issue any more, they can keep it open, there’s nothing there.”

The investigation was launched after a French TV crew filmed U.S. Postal officials disposing of medical waste far from the team hotel during the 2000 Tour.

French officials expect the probe to close by the end of the summer.

The 30-year-old Armstrong has never failed a drug test and denies taking banned substances.

Immediately after Sunday’s climb up the Mont Ventoux, when hecklers shouted at him, Armstrong said the jeering was “an indication of their intelligence.” But later he said the problem was “blown out of proportion.”

“You’re talking about a few people,” Armstrong said. “It got bad on Ventoux, but that was just 20 percent of the people. It’s not as bad as it got made out to be.”

Armstrong said doping suspicions among the media and the public were becoming so widespread that athletes’ credibility was being unfairly undermined.

“It’s an epidemic, it’s going to spread,” he said. “When somebody breaks the 5,000-meter record in track, they’re going to question it. It’s going to grow and grow and grow. You’re going to have this room of cynics, of people saying, ‘It’s just not possible.’

“In that sense, the champions and the record breakers and the best will never be vindicated.”

Armstrong is expected to extend his lead in Saturday’s individual time trial from Regnie-Durette to Macon. The three-week race ends Sunday in Paris.

As he closes in on winning the Tour de France, Armstrong also said he plans on returning to try to equal the event record of five titles, even though it is becoming difficult to leave his family.

“It’s harder and harder to be away from home with a wife and three children,” Armstrong said. “My girls started crawling while I was away at the Tour de France.

“But it’s not my last Tour de France.”

Four riders Jacques Anquetil and Bernard Hinault of France, Eddy Merckx of Belgium, and Miguel Indurain of Spain share the record of five titles. Only Indurain took all five in a row.

Armstrong would not say whether he’s aiming to become the most successful rider in Tour history by winning six straight titles.

“I would never say that it would be suicide to announce that,” Armstrong said. “I love what I do, I feel strong. I don’t think I’m getting weaker, but it’s hard to win this race, so many things can happen.”

If Armstrong wins Sunday, this will have been one of his easiest victories since returning from testicular cancer to win his first Tour title in 1999.

Armstrong said he was glad he had no rival strong enough to seriously challenge him.

“I sleep pretty good at night with the lead that we have,” Armstrong said. “I don’t know how well I’d sleep with a 30-second lead going into the final time trial.

“So I’m going to have to vote for good sleep. And I will sleep good the rest of my life having had it that way. I wouldn’t consider it an empty challenge or an empty race or an empty career.”