The World Anti-Doping Agency said on Wednesday that another batch of athlete data has been leaked by the same Russian cyber espionage group that published confidential data earlier this week.
This time, WADA said the hackers released data of 25 athletes from the United States, Germany, Britain, Czech Republic, Denmark, Poland, Romania, and Russia.
The hacking group, known as APT28 and Fancy Bear by US cyber-security researchers, was also blamed by WADA on Tuesday for posting data about US athletes Simone Biles, Elena Delle Donne, and Serena and Venus Williams.
"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 that have been targeted; and cause apprehension for all athletes that were involved in the Rio 2016 Olympic Games," WADA Director General Olivier Niggli said in a statement.
"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."
WADA said it believed the hackers gained access to its anti-doping administration and management system (ADAMS) via an IOC-created account for the Rio Games.
According to WADA, the account includes confidential medical data such as Therapeutic Use Exemptions, which are issued by sports federations and national anti-doping organizations to allow athletes to take certain substances.
WADA said it is reaching out to the national anti-doping organisations and international federations whose athletes are impacted by the latest data release to provide support.
WADA also repeated its belief the attacks are being carried out as retaliation for the agency's investigations that exposed state-sponsored doping in Russia.
The agency's independent McLaren report, released in July, charged that Russians had swapped positive doping samples for clean ones during the 2014 Sochi Olympics, with the support of the Russian secret service.
A separate anti-doping commission report released last November that was headed by former WADA president Dick Pound, alleged widespread corruption and collusion that added up to a state-sponsored drugs culture in Russian athletics.
"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 Pound and McLaren investigations that exposed state-sponsored doping in Russia,” said Niggli.
"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 program in Russia."