Kohl won the King of the Mountains jersey and finished third overall

Climbing specialist Bernhard Kohl has become the latest Tour de France competitor to fail a doping test.

The Austrian won the King of the Mountains jersey as the best climber on this year's Tour and was third overall.

But France's national anti-doping agency (AFLD) confirmed Kohl had become the fourth rider to test positive for Cera, a version of blood booster EPO.

Kohl's Gerolsteiner team-mate Stefan Schumacher, plus Leonardo Piepoli and Riccardo Ricco, also failed Cera tests.

"I had a phone call from Bernhard Kohl and he admitted he was notified with the news of a positive test," Gerolsteiner team manager Hans-Michael Holczer told the Reuters news agency.

Kohl took third overall behind winner Carlos Sastre and Cadel Evans in one of the closest podium finishes in the 105-year history of the race.

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France's national anti-doping agency (AFLD) revealed in September that it would be re-testing blood samples from some riders after it discovered a more effective test for Cera.

Ricco tested positive for the blood-boosting drug during the race, and on 6 October, his fellow Italian and Saunier Duval team-mate Piepoli was also revealed to have used Cera, along with Schumacher.

Just a week later, the Tour, which has been persistently dogged by doping scandals, has been rocked by the news of Kohl's failed test.

An AFLD statement said: "The AFLD confirms that its laboratory at Chatenay-Malabry has found two abnormal samples showing the presence of EPO Cera in blood tests done on 3 and 15 July, before and during the Tour de France, on Austrian cyclist Bernard Kohl."

The Gerolsteiner team will disband at the end of the year, while Kohl had signed a three-year contract with Silence.

Ricco, who has been banned for two years, and Piepoli were sacked by Saunier Duval in July, the latter for "violation of the team's ethics code".

The AFLD has not said whether it has now completed the re-testing of samples, leaving open the possibility of more positive results.

Two other riders, Spaniards Manuel Beltran and Moises Duenas Nevado, tested positive for an older version of EPO during the Tour itself, and Kazakhstan's Dmitri Fofonov failed a test after stage 18 for heptaminol.

The discovery of a new test for Cera has prompted the International Olympic Committee to retest 5,000 samples from the Beijing Games.