Chris Froome had double the allowed limit of an asthma drug in his system during the Vuelta a Espana in September.
The UCI has requested more details after the results from a urine sample.
Froome won the Vuelta title following his Tour de France victory in July.
Analysis indicated the presence of Salbutamol at a concentration of 2,000 nanograms per millilitre, compared with the WADA threshold of 1,000 nanograms per millilitre.
The Englishman says he followed the team doctor's advice to increase his Salbutamol dosage.
In a statement Team Sky were quick to point out that the "notification of the test finding does not mean that any rule has been broken".
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 Dave Brailsford added: “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.”
