Four-time Tour de France winner Chris Froome has been required by cycling's governing body to provide information after he returned an abnormal doping test at the Vuelta.
Froome's Team Sky said in a statement that Froome has been informed by the UCI that a urine test on Sept. 7 revealed a concentration of salbutamol of 2,000 nanograms, twice the threshold of 1,000.
Sky said that the Kenyan-born British rider had to take an increased dosage of salbutamol after he "experienced acute asthma symptoms" during the final week of the race.
Froome said: "The UCI is absolutely right to examine test results and, together with the team, I will provide whatever information it requires."
After successfully defending his Tour de France title in July, Froome went on to win the Spanish Vuelta for the first time.
According to the Team Sky statement, Chris Froome said:
"It is well known that 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 sure that 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 is absolutely right to examine test results and, together with the team, I will provide whatever information it requires."
Team Principal Sir Dave Brailsford said:
"There are complex medical and physiological issues which affect the metabolism and excretion of Salbutamol. We're committed to establishing the facts and understanding exactly what happened on this occasion.
"I have the utmost confidence that Chris followed the medical guidance in managing his asthma symptoms, staying within the permissible dose for Salbutamol. Of course, we will do whatever we can to help address these questions."