PARIS – Italian cyclist Leonardo Piepoli twice tested positive for an advanced blood booster during this year's Tour de France, officials said Monday, and German cyclist Stefan Schumacher's team suspended him for suspected use of the same substance.

The two became the second and third riders to test positive for CERA, an advanced version of the blood booster EPO, at this summer's Tour. Italian cyclist Riccardo Ricco has already admitted to CERA use.

Between them, the three riders won five stages during the July race – or about a quarter of the 21 stages at cycling's premiere race, which has struggled to maintain its credibility after being rocked by doping scandals three years in a row.

The French Anti-Doping Agency has been retesting blood samples from the race in a bid to catch more cyclists they suspect may have used CERA. The original urine tests had cast a shadow of doubt over several riders but proved inconclusive.

This year's Tour was run under the auspices of the French cycling federation, and it will be responsible for eventually revising the results of this year's race after disciplinary procedures are completed against any riders found to have cheated, Tour organizers said Monday.

Italian and French officials said Monday that Piepoli twice tested positive during the Tour, and the Italian Olympic Committee said he has been summoned for a hearing Friday. If found guilty of doping, he would face a two-year ban.

Piepoli, who won the punishing 10th stage through the Pyrenees, was fired by Saunier Duval in July for violating the team's ethical code, but Monday marked the first time officials confirmed he had tested positive.

The Italian committee and French anti-doping agency said Piepoli failed tests on July 4 and July 15 for CERA. Pierre Bordry, head of the French anti-doping agency, confirmed that he had notified the Italian committee of Piepoli's positive tests.

Ricco, Piepoli's former Saunier Duval teammate, was banned for two years by the Italian Olympic Committee last week after admitting to doping during the Tour. Ricco won the sixth and ninth stages of the Tour in spectacular fashion – the second victory coming with a long solo breakaway on one of the race's toughest mountain stages.

Also Monday, Hans-Michael Holczer, the head of Schumacher's Gerolsteiner team, said he had received confirmation from the Tour's director that the cyclist had “tested positive for CERA.” He said he had suspended the rider immediately.

The head of the French anti-doping agency said he could not immediately confirm the result.

Germany's cycling federation said it would move to take action against Schumacher, who won both individual time trials at the Tour and held the race lead for two days.

“The proceedings, with the aim of the highest possible ban, will be opened on Tuesday,” federation president Rudolf Scharping said.

The announcements were the latest blow to the Tour. The 2006 and 2007 races were rocked by doping scandals, and several riders had previously tested positive during this year's race, which was won by Carlos Sastre of Spain.

Some sponsors and television companies ended their deals – and others followed suit after this year's Tour.

Associated Press writer Geir Moulson in Berlin contributed to this report.