The Orica-GreenEdge rider tested positive for Terbutaline on the final stage of the French race with the team doctor failing to apply for a Therapeutic Use Exemption (TUE).
Orica-GreenEdge released a statement regarding the positive test explaining it takes full responsibility. The UCI confirmed the case and clarified that because Terbutaline does not spark a provisional suspension, Yates is free to continue to race until any eventual sanction is decided.
"On April 22, the team was notified that Simon Yates has an adverse analytical finding from a test conducted at Paris-Nice, stage 6 on March 12, 2016," read the team statement.
"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.
"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 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."
A British Cycling spokesman told Cyclingnews, "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."
Yates, 23, from Bury, England, turned professional in 2014 with Orica-GreenEdge and is the twin brother of Adam Yates. He took part in the Tour de France during his debut season as a professional rider and picked up a number of promising stage race results.
Cyclingnews attempted to contact Yates and several members of the Orica-GreenEdge set-up. No one was available for comment.