Sir Bradley Wiggins and Chris Froome are among athletes whose medical information has been leaked after hackers stole files from the World Anti-Doping Agency (Wada).
The details of five Team GB athletes were leaked in this second batch of data stolen by a cyber-espionage group calling itself Fancy Bears, believed to be from Russia.
American and German athletes are also among those whose details have been released in the leak.
According to Sky News, there has been no suggestion the athletes involved had done anything wrong.
According to BBC sports editor Dan Roan, Chris Froome said in a statement: “I’ve openly discussed by TUEs with the media and have no issues with the leak which only confirm my statements.
“In 9 years as a professional I’ve twice required a TUE for exacerbated asthma, the last time was in 2014.”
Wada first fell victim to the hackers on Tuesday when medical records relating to “therapeutic use exemptions” (TUEs) granted to certain athletes were made public.
TUEs allow the use of certain banned substances because of an athlete’s specific verified medical needs.
Fancy Bears claims that the exemptions are “licenses for doping” and has labelled Wada “corrupt and deceitful”, according to the BBC.
US tennis stars Venus and Serena Williams and gymnast Simone Biles were among those affected in the initial leak.
The body confirmed on Thursday that another leak of “confidential athlete data” had taken place, the Press Association reported.
In a statement, Wada said: “Fancy Bear [aka Tsar Team (APT28)] have leaked another batch of confidential athlete data from Wada’s Anti-Doping Administration and Management System (ADAMS).
“Similar to the leak that the agency announced on 13 September, this time the group released the confidential athlete data of 25 athletes, from eight countries, into the public domain.
“The targeted athletes include 10 from the United States, five from Germany, five from Great Britain, one from the Czech Republic, one from Denmark, one from Poland, one from Romania, and one from Russia.”
The organisation revealed that hackers had illegally gained access to its anti-doping administration and management system database via an International Olympic Committee-created account for the Rio Games.
Wada director general Olivier Niggli said: “Wada is very mindful that this criminal attack, which to date has recklessly exposed personal data of 29 athletes, will be very distressing for the athletes targeted and cause apprehension for all athletes that were involved in the Rio 2016 Olympic Games.
“To those athletes that have been impacted, we regret that criminals have attempted to smear your reputations in this way and assure you that we are receiving intelligence and advice from the highest level law enforcement and IT security agencies that we are putting into action.
“Given this intelligence and advice, Wada has no doubt that these ongoing attacks are being carried out in retaliation against the Agency, and the global anti-doping system, because of our independent (Dick) Pound and (Richard) McLaren investigations that exposed state-sponsored doping in Russia.
“We condemn this criminal activity and have asked the Russian government to do everything in their power to make it stop.
“Continued cyber-attacks emanating from Russia seriously undermine the work that is being carried out to rebuild a compliant anti-doping programme in Russia.
“We still believe access to ADAMS was obtained through spear phishing of email accounts, whereby, ADAMS passwords were obtained enabling access to ADAMS account information confined to the Rio 2016 Games.
“We have no reason to believe that other ADAMS data has been compromised.”