British cyclist Simon Yates has failed an in-competition drugs test - with his team blaming an "administrative error" over the use of an asthma inhaler.
Orica-GreenEdge said they took "full responsibility for the mistake" and there was "no wrongdoing" by Yates.
They added that he tested positive for the banned substance terbutaline and a team doctor failed to apply for a therapeutic use exemption (TUE).
They also said Yates will get their full support during the investigation.
"This is solely based on a human error that the doctor in question has taken full responsibility for," the Australian team added.
Yates, a former points race world champion, is regarded as one of Britain's brightest prospects on the road, along with his twin brother Adam. He is a strong contender to make the TeamGB road race team for the Rio 2016 Olympics this summer.
The sport's governing body, the UCI, notified British Cycling of a "potential anti-doping rule violation" at the Paris-Nice race in March.
Proceedings will be managed by the UCI independently, according to a spokesman for British Cycling.
"It would be inappropriate to comment further until the process has been completed," the spokesman added.
Yates, a climber with Orica, achieved a top-10 finish on the Mur de Huy stage of last year's Tour de France and was seventh in last month's Paris-Nice race.
The team are "concerned by the leak" of the failed test and are now submitting all evidence to the UCI.
News of the failed test is another blow in a bad week for British Cycling.
Technical director Shane Sutton resigned on Wednesday amid claims of sexism and discrimination. British Cycling is investigating claims the 58-year-old Australian used derogatory words to describe Para-cyclists, while an independent review will also look into rider Jess Varnish's accusations that Sutton made sexist comments and told her to "go and have a baby".
Sutton "rejects the specific claims" but said the allegations against him had "become a distraction" to British athletes before this summer's Rio Olympics.
A third inquiry was ordered on Thursday, with separate claims that official British Cycling kit was available to buy online. British Cycling denied any equipment provided by UK Sport had been given away or sold on for profit but said other unwanted kit from commercial partners is sold or given away.
Sutton was also asked to attend a meeting on Tuesday to discuss the kit allegations, revealed in the Daily Mail. UK Sport, which helps fund Britain's Olympians and Paralympians, ordered the investigation to "protect our investment in all sports on the world-class programme".
BBC sports editor Dan Roan
"This is now in danger of turning into the worst week in the history of British Cycling. Today sees the start of the sport's showpiece UK event - the Tour de Yorkshire -with more than a million people expected to watch the action. But it risks being overshadowed by a mounting crisis at the embattled national governing body.
"First came the damaging sexism and bullying allegations that cost head coach Shane Sutton his job. Then the revelation British Cycling was unaware Sutton was also being paid by Team Sky, followed by an investigation into whether team kit and bikes had been unofficially sold on.
"Now another grave blow, with rising star Simon Yates, expected to be part of TeamGB in Rio, failing a drugs test. All this just three months out from the Games. The timing could not be worse.
"For British Cycling, so often heralded in recent years for its record in both performance and participation, these are unusually dark days."