Chris Froome (Team Sky) has returned an “adverse analytical finding” for Salbutamol in a urine sample taken at this year’s Vuelta a Espana.

The sample, which was taken after stage 18 of the Vuelta — a race Froome went on to win — contained 2,000 nanograms per millilitre (ng/ml) of Salbutamol, twice the 1,000 ng/ml permitted by the World Anti Doping Agency (WADA).

An analysis of Froome’s B sample confirmed the results of the A sample and, according to the UCI, “proceedings are being conducted in line with the UCI Anti-Doping Rules”.

Salbutamol is a common medication used to relieve the symptoms of asthma and is permitted for use without a therapeutic use exemption, up to a threshold. Froome reportedly experienced “acute asthma symptoms” during the Vuelta a Espana, requiring further medication.

“It is well known that I have asthma and I know exactly what the rules are,” Froome said via a Team Sky press release. “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 Sky principal Dave Brailsford said the team is “committed to establishing the facts and understanding exactly what happened on this occasion”.

“There are complex medical and physiological issues which affect the metabolism and excretion of Salbutamol,” Brailsford continued. “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.”

As explained by the UCI, Froome will now be required to explain the finding:

“The presence in urine of Salbutamol in excess of 1000 ng/mL … is presumed not to be an intended therapeutic use of the substance and will be considered as an Adverse Analytical Finding (AAF) unless the Athlete proves, through a controlled pharmacokinetic study, that the abnormal result was the consequence of the use of the therapeutic dose (by inhalation) up to the maximum dose indicated above.”

According to the UCI, Froome is not required to serve a provisional ban: ” 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.”

If Froome isn’t able to explain the finding, he could face a stint on the sidelines. In January 2015, Diego Ulissi was handed a nine-month ban after testing positive for Salbumatol at the 2014 Giro d’Italia. Ulissi was found to have 1,900 ng/ml of the substance in his urine, 100 ng/ml less than the amount detected in Froome’s sample. Likewise, Alessandro Petacchi faced a one-year ban in 2008 after returning a sample with 1320 ng/ml of Salbutamol.