Chris Froome could be banned and stripped of his Vuelta title after a drugs test produced an “adverse analytical finding” during the race in September.
Froome, who became only the third winner of the Tour de France-Vuelta double in the same season, had twice the allowed amount of asthma drug Salbutamol in his body than permitted by the World Anti-Doping Agency.
If the 32-year-old and Team Sky are unable to explain the results then he faces a possible ban and losing the title. The rider and team have known about the finding - from a urine sample on September 7 - since the 20th of the month, the day he won bronze in the World Championships individual time trial in Bergen, Norway.
The team’s medics and lawyers have been arguing the case with cycling governing body, the UCI, with no timeframe on when a conclusion might be reached.
As an asthmatic, Froome is permitted to take Salbutamol but WADA rules say there can only be 1,000 nanograms per millilitre (ng/ml) in the system compared to the 2,000 ng/ml that were found in the sample taken after stage 18 which ended in Santo Toribio de Liebana in northern Spain.
It is believed Sky are trying to prove in a laboratory that neither Froome nor team doctor Derick MacLeod, who will also work with Team GB at the Winter Olympics in PyeongChang, flouted the rules and that the rider might excrete excess levels of the substance despite taking permitted amounts.
Sky have pointed out that none of the other samples taken at either the Tour or the Vuelta was questionable.
In a statement this morning, Froome said: “It is well known I have asthma and I know exactly what the rules are. I use an inhaler to manage my symptoms (always within the permissible limits) and I know for use I will be tested every day I wear the race leader’s jersey.
“My asthma got worse at the Vuelta so I followed the team doctor’s advice to increase my Salbutamol dosage. As always, I took the greatest care to ensure that I did not use more than the permissible dose.
“I take my leadership position in my sport very seriously. The UCI are absolutely right to examine test results and, together with the team, I will provide whatever information it requires.”
He later tweeted: “Thank you for all the messages of support this morning. I am confident we will get to the bottom of this. Unfortunately I can’t share any more information than I already have until the enquiry is complete.”
The UCI statement in full
"The Union Cycliste Internationale (UCI) confirms that British rider Christopher Froome was notified of an Adverse Analytical Finding (AAF) of Salbutamol in excess of 1000ng/ml (*) in a sample collected during the Vuelta a Espana on 7 September 2017. The rider was notified of the AAF on 20 September 2017.
"The anti-doping control was planned and carried out by the Cycling Anti-Doping Foundation (CADF), the independent body mandated by the UCI, in charge of defining and implementing the anti-doping strategy in cycling.
"The analysis of the B sample has confirmed the results of the rider's A sample and the proceedings are being conducted in line with the UCI Anti-Doping Rules.
"As a matter of principle, and whilst not required by the World Anti-Doping Code, the UCI systematically reports potential anti-doping rule violations via its website when a mandatory provisional suspension applies. Pursuant to Article 7.9.1. of the UCI Anti-Doping Rules, the presence of a Specified Substance such as Salbutamol in a sample does not result in the imposition of such mandatory provisional suspension against the rider.
"At this stage of the procedure, the UCI will not comment any further on this matter."