|Kolobnev at the official presentation of riders before the Tour de France began [AFP]
A search of the hotel room of the Russian rider who failed a doping test during the Tour de France revealed no banned substances, a French official said on Tuesday.
Jean-Pascal Violet, the public prosecutor for the town of Aurillac, told the Associated Press news agency he had opened an investigation in connection with the incident involving Katusha cyclist Alexandr Kolobnev.
Kolobnev dropped out of the Tour on Monday after the International Cycling Union (UCI) said a urine sample collected from him last Wednesday tested positive for Hydrochlorothiazide, a diuretic that can also be used as a masking agent.
He was in 69th place heading into Tuesday's 10th stage, but Katusha said on Monday he was out of the Tour after deciding to "suspend himself according to UCI rules."
The Russian issued his own statement on Tuesday in which he said he would not comment on the situation "for respect to the race organizers and cycling in general."
Kolobnev said he doesn't know how the banned diuretic got into his urine sample, and that he was waiting for the results of a test of his B sample.
He became the first rider to exit this year's Tour de France for doping reasons.
The UCI, confirming the rider's positive test, issued a statement reporting: "The UCI has informed the Russian rider Alexandr Kolobnev of an abnormal finding (presence of Hydrochlorothiazide according to a report submitted by the WADA-accredited laboratory in Chatenay-Malabry) from a urine sample taken during the Tour de France on July 6, 2001.
"M. Kolobnev has the right to request analysis of a B sample and to be present during the process."
Under UCI rules Kolobnev could have continued to race because the banned diuretic is classed as a "specific substance" by the UCI.
The statement added: "The UCI's anti-doping rules do not foresee a provisional suspension given the nature of the substance, which is a 'specified substance'.
"However the UCI is confident that his team will take the necessary measures to ensure the serenity of the Tour de France and at the same time give the rider a chance to prepare his defence, notably with respect to the reglementary four day period in which he is obliged to proceed with the analysis of a B sample."
The Russian outfit said he would be sacked if the B sample was also Positive and be fined a sum five times his salary.
"Team Katusha rider Alexandr Kolobnev, after testing positive for a diuretic at a medical examination during the Tour de France's first week, decided to suspend himself according to UCI rules, waiting for the B-sample," said Katusha's statement.
"At the moment, Team management and the rider have no further comment. It has to be noticed that internal rules in Team Katusha say that the rider, if the B-sample also tests positive, will be fired and will have to pay five times his salary as a fine."
After the news broke Kolobnev was seen leaving his team hotel in nearby Vezac in one of two Katusha team cars which were being escorted away by two police cars.
The 30-year-old Kolobnev, a silver medal winner at the 2009 world road championships, was placed 69th in the overall Tour de France standings, 22min 15sec behind yellow jersey leader Thomas Voeckler.
Kolobnev, a multi-national champion, is also a respected one-day classics rider who finished fourth in the Olympic road race in Beijing at the 2008 Games.
Australia's former top cricket star Shane Warne tested positive for Hydrochlorothiazide along with amiloride in February 2003, prompting him to pull out of the World Cup.
He was given a 12-month ban by the Australian Cricket Board's anti-doping unit.