Christophe Ena, Associated Press
Cadel Evans, wearing the leader's yellow jersey, is followed by Christian Vandevelde of the U.S. during Friday's 13th stage of the Tour de France.

NIMES, France — In a race thrown into turmoil by drugs, Britain's Mark Cavendish won a stage for the fourth time and Australia's Cadel Evans kept the yellow jersey Friday as the Tour de France tried to recover from another scandal.

This was the second straight stage victory for Cavendish. Leading a group sprint, the Team Columbia rider beat Australia's Robbie McEwen by nearly two bike lengths in the hot and windy ride, with France's Romain Feillu third.

"The first stage win was my favorite; today's was the hardest," Cavendish said after the 113-mile run from Narbonne to Nimes. "Every win's a win."

Evans retained the overall lead by finishing alongside his main rivals in the main pack. He leads Frank Schleck of Luxembourg by one second and Christian Vande Velde of the United States by 38.

Italy's Riccardo Ricco on Thursday became the third rider to test positive for the banned performance enhancer EPO, prompting his Saunier Duval team to quit the race and fire him the next day. Ricco was held overnight for police questioning.

Saunier Duval also fired Leonardo Piepoli, an Italian who won the 10th stage for "violation of the team's ethical code." The team declined to elaborate.

French judicial officials filed preliminary charges Friday against Ricco, citing "use of a toxic substance." He was released under judicial watch and ordered not to speak to anyone from his team. Antoine Leroy, French state prosecutor for the town of Foix, said Ricco contested the claim that he had used EPO.

A police search of a hotel room where Ricco had stayed turned up medical equipment, such as syringes, catheters and medical bags, but no doping products, Leroy said.

Ricco, the Giro d'Italia runner-up, won the sixth and ninth stages. He was the biggest name among the three riders who tested positive for EPO during this year's Tour.

The head of France's anti-doping agency, Pierre Bordry, said Ricco had tested positive for CERA (continuous erythropoietin receptor activator), an advanced version of EPO.

Mircera, the brand name for CERA made by Swiss-based Roche Holdings, helps users produce more red blood cells, company spokeswoman Claudia Schmitt said. It received U.S. and European approvals last year as a treatment for anemia caused by kidney failure. The substance remains much longer in the body than regular EPO.

Schmitt said Roche has provided information about the treatment to the World Anti-Doping Agency, which has banned EPO for athletes. Roche wants the drug used by patients only, she said.

Spanish riders Moises Duenas Nevado and Manuel Beltran were also ejected from the Tour this year for using EPO.

Bordry said Piepoli was one of several riders targeted because he had suspicious blood parameters in pre-Tour blood tests July 4 and 5 and because of "information from outside sources." Bordry would not elaborate on those sources, saying only that he was awaiting test results on Piepoli and other riders.

A French law took effect this month that makes anyone who produces, transports, acquires or possesses doping products liable for up to five years in prison and a $119,000 fine.

This marks the first time athletes who take drugs can be liable in the justice system. Previously, possession of a doping product was not illegal.

Some critics said the law was too tough, and athletes should be punished with sports sanctions, not legal sanctions.