In a report from David Walsh, one the key figures in the investigation that eventually exposed Lance Armstrong as a drugs cheat, it is claimed that the UCI have written to 2012 Tour of Britain winner Jonathan Tiernan-Locke asking him for clarification into blood values dating back to September lasy year.
British rider Tiernan-Locke joined Team Sky at the start of the season but the suspect samples date from before he joined the team.
The Devon-born cyclist was selected to represent Great Britain at Sunday's world championship road race in Florence but withdrew citing 'lack of form.'
Team Sky’s principal Sir Dave Brailsford told the Sunday Times: "I'm not in a position to say anything at this point."
Walsh's piece notes that: "According to Sunday Times sources, Tiernan-Locke’s problem arises from variations in his biological passport data, which have been irregular enough to cause the UCI authorities to begin the investigation process.
"(He) has three weeks from the time he received the letter to offer an explanation for the variations in his blood values. His response will then be assessed by the same three-man panel of experts that made the original decision to investigate. If they are not satisfied by the rider’s response, they will pass the case to a panel of 11 experts who will decide whether the rider should be disciplined."
Team Sky have a 'zero tolerance' policy towards doping and following the Lance Armstrong scandal, the British team asked riders and support staff to sign up to a written statement saying they had no past or present involvement with drugs.
At that time, sports director Steven de Jongh and race coach Bobby Julich quit after admitting to taking banned substances earlier in their careers.
Tiernan-Locke competed for the Endura team last season but as they mainly competed in cycling's lower tiers, their riders were not part of the biological passport data system.
However, Tiernan-Locke won the Tour of Britain in 2012 and after that victory he began to have regular blood tests.
The Sunday Times notes that French newspaper L'Equipe raised questions about his form last season after he won the Tour du Haut Var and the Tour Mediterranean.
"Are we in the presence of a champion or a chimera?" the paper wrote at the time.
"Tiernan-Locke can only be one or the other to win five races in a row. He’s part of a team from the third division, a category where the riders don’t have to submit to biological monitoring, via the blood passport programme of the Union Cycliste Internationale."