British cyclist Simon Yates has failed an in-competition anti-doping test following a doctor's error, his team have announced.
Orica-GreenEdge have accepted responsibility for Yates' positive test for Terbutaline, which is used to relieve asthma symptoms.
The Australian team admitted an administrative error led to the medicine being administered without the required therapeutic user exemption certificate.
A statement from Orica-GreenEdge read: "There has been no wrong-doing on Simon Yates' part.
"The team takes full responsibility for this mistake and wishes to underline their support for Simon during this process."
The team were made aware of the positive test on April 22, following a test conducted on March 12, at stage six of Paris-Nice. He finished sixth on the stage.
The statement added: "The positive result is for the substance Terbutaline. The substance was given to Simon Yates in the form an asthma inhaler and accordingly, this was noted by the team doctor on the doping control form, signed at the time of the test.
"The substance was given in an ongoing treatment of Simon Yates' documented asthma problems. However, in this case the team doctor made an administrative error by failing to apply for the TUE required for the use of this treatment.
"The use of Terbutaline without a current TUE is the reason it has been flagged as an adverse analytical finding. This is solely based on a human error that the doctor in question has taken full responsibility for."
The 23-year-old Yates won gold in the points race at the 2013 Track World Championships in Minsk, is among Britain's brightest prospects.
He made his Tour de France debut in 2014 and raced again in 2015, after opting to sign for Australian squad Orica-GreenEdge ahead of Team Sky.
Yates is the older twin and his brother Adam also races for Orica-GreenEdge and Britain. They are not related to former rider Sean Yates.
Simon Yates finished 2015 as the best young rider in the Criterium du Dauphine and Tour of the Basque Country. He also finished eighth on stage three of the Tour de France, which finished atop the Mur de Huy in Belgium.
A strong climber, he was a contender to ride in the Rio Olympics road race.
Orica-GreenEdge say they are attempting to clarify the situation with the UCI. Cycling's world governing body was not available for comment early on Friday morning.
"The team is concerned by the leak of this information and has no further comments until there has been a full evaluation made of the documentation, statements and evidence that the team and Simon Yates are now submitting to the UCI in order to clarify everything," the Orica-GreenEdge statement added.
British Cycling, the sport's embattled national governing body, confirmed the positive test, but did not name Yates.
It was the latest negative story in a week which has seen Shane Sutton resign as technical director following allegations of discrimination. He denies the claims.
A British Cycling spokesman said: "British Cycling can confirm that it has been notified by the UCI of a potential anti-doping rule violation against a British rider based on an analysis of a sample provided in-competition.
"As with any other doping violation charge at this level, those proceedings will be managed independently of British Cycling by the UCI.
"It would be inappropriate to comment further until the process has been completed."
A UK Anti-doping spokeswoman said: "UK Anti-Doping does not discuss or disclose details of any cases until due legal process has been completed and an anti-doping rule violation is deemed to have been committed. Once the legal process is complete, details of all anti-doping rule violations are published on our website."