UK Anti-Doping has said it is examining an "allegation of wrongdoing within cycling".
The announcement came as the Daily Mail reported UKAD is investigating Team Sky and Sir Bradley Wiggins over the contents of a medical package.
The newspaper alleges a package was delivered to Team Sky in France on June 12, 2011, and it reports that UKAD is looking at what that contained.
UKAD, which is dedicated to protecting a culture of clean sport, did not go into any detail about the allegation it is looking at and mentioned no names.
A spokeswoman for UKAD said in a statement: "UK Anti-Doping is investigating an allegation of wrongdoing within cycling. In order to protect the integrity of the investigation, we will not comment further."
Wiggins won the Dauphine Libere cycling race on the day the package was reportedly delivered, completing victory in the eight-day event after the final stage from Pontcharra to La Toussuire.
According to documents leaked by Russian hacker group Fancy Bears, Wiggins had a therapeutic use exemption (TUE) for triamcinolone acetonide - a synthetic corticosteroid - which was effective from June 29, 2011. Any use of a banned substance requires an active TUE.
The Daily Mail reports that while British Cycling has not identified the substance in the package, it has indicated it did not contain triamcinolone.
Wiggins and Team Sky have strenuously denied any wrongdoing since it emerged the 2012 Tour de France winner has received six TUEs during his career, insisting each time the exemptions were medically necessary due to asthma and pollen allergies.
A host of major names from world sport have seen hacked personal information released into the public domain recently, although the World Anti-Doping Agency indicated earlier this week that Fancy Bears may have doctored or fabricated some of the medical documents it has released.
United States Anti-Doping Agency chief executive Travis Tygart has labelled the Fancy Bears "con artists" after the hackers accused US sports officials of covering up doping.
The Russian group on Thursday released email exchanges that it claimed revealed that "USADA covers up many athletes using prohibited substances".
Tygart hit back by dismissing the group's latest release as "desperate" and "malicious".
"This is just another desperate attempt to distract from the real issue of (Russian) state-sponsored doping," Tygart told BBC Sport.
He said the Fancy Bears were trying to "smear the reputations of athletes and organisations from around the world who choose to operate with integrity and abide by the rules".
"They are con artists," he added. "We are confident that people will see this for what it is: a malicious and illegal invasion of athlete privacy followed by a baseless smear campaign."
Source: PA-WIRE
