However the IOC-accredited laboratory at Chatenay-Malabry on the outskirts of Paris said the "typing error" was a blip that had no bearing on their finding testosterone in both A and B samples taken after stage 17 of the race.

Former Phonak team rider Landis has always protested his innocence in the affair and is basing his defence ahead of an anticipated ban from the sport on what he believes are inconsistencies on the part of the French lab.

On Wednesday the laboratory admitted, following a report in Le Monde, that a labelling error had been made.

But French newspaper Le Monde reported on Wednesday that the B sample had "ill-advisedly been indexed with the wrong number on the accompanying report".

The newspaper report added: "The identification number of Floyd Landis was 995 474 while on the report it was listed as 994 474.

"That doesn't signify that the B sample did not belong to the American. But it will be seized upon by his lawyers who will try to bring new elements to his (defence) case at a presentation on Friday."

Landis confirmed on Tuesday he will unveil an updated version of his appeal to overturn the positive doping test on Friday, which will be directed by his physician Arnie Baker at the Tucson Convention Centre in Arizona.

Laboratory director Jacques de Ceaurriz later confirmed to AFP the error had been made, but said it was a minor detail.

"It's an error as regards numbering, a typing error which has no significance whatsoever on the findings in the samples," said de Ceaurriz, adding that the World Anti Doping Agency (WADA) was aware of the incident.

"These little mistakes happen. They are corrected, and noted."

De Ceaurriz added: "It wouldn't surprise me that Landis' lawyers use this information.

"But the error does not wipe out the result of the analysis."

On Tuesday an enquiry was launched after hackers pirated the computer system at the French laboratory.

De Ceaurriz confirmed to AFP that an investigation was under way after the discovery that their computer system had been accessed from outside.

"An enquiry is under way. I'm not making any comment because the incident is probably linked to affairs currently being handled by the laboratory," de Ceaurriz told AFP.

"We have been aware of this for some time and in the past week our suspicions have been confirmed," he added.

According to French sports daily l'Equipe, police have identified an alleged suspect based on emails and letters sent by the individual, who is reported to be close to Landis, in which he cited internal documents to condemn testing errors by the laboratory.