Paris prosecutors on Tuesday revealed that they have launched an investigation after the discovery of suspicious medical equipment including "syringes and drips" during the Tour de France in July.
The inquiry will be carried out by police officers from the Centre for the Prevention of Damage to the Environment and Public Health (OCLAESP), prosecutors added.
The probe was launched last July after the organisation responsible for the disposal of medical waste produced by the Tour de France teams discovered "suspicious medical equipment," a judicial source said.
The source added that "hundreds" of syringes had been recovered, while the OCLAESP also seized medical items from hotels in which some of the riders stayed during the race.
According to French daily Le Monde, the investigation involves a number of teams including Astana, home of 2009 Tour de France champion Alberto Contador of Spain and American seven-time winner Lance Armstrong.
Sports daily L'Equipe backed up Le Monde's claims regarding Astana, and added that some of the syringes being analysed had been used by the Kazakh team.
"These syringes, used by the team of race winner Alberto Contador, were sent to the Parisian forensics laboratory Toxlab of Professor Gilbert Pepin and are currently being analysed to determine their contents," read an article on the L'Equipe website.
Astana issued a brief statement insisting it had nothing to hide.
"Astana Cycling Team is surprised to read in the French press that the team is involved in an investigation by French prosecutors into doping.
"These media reports are the first we as a team have heard of an investigation. According to the press articles, the investigation involves a number of cycling teams having participated in the 2009 Tour de France.
"The Astana Cycling Team has nothing to hide, the riders use no forbidden substances, the Team is confident in the result of analyses performed or to be performed by a Parisian laboratory and is prepared to cooperate," the statement concluded.
On October 7, the French Anti-doping Agency (AFLD) indicated that officials had found "incongruous" substances in bins used by the Tour de France teams, but nothing that contradicted the global anti-doping code.
According to the AFLD, sitagliptin, which is used by diabetics when injecting insulin, and valpromide, an anti-convulsant which is prescribed in the treatment of epilepsy and manic depression, featured in a "surprising medicinal arsenal".
At the same time, the AFLD accused the International Cycling Union (UCI), its partner during anti-doping tests at the Tour de France, of showing "preferential treatment" to Astana.
The UCI rejected the accusations and described them as "completely unfounded".
The route of the 2010 Tour de France, which will begin in the Dutch city of Rotterdam, will be unveiled on Wednesday.