Williams sisters, Simone Biles, others listed by hackers after WADA data breach

MONTREAL, Sept. 13 (UPI) -- The World Anti-Doping Agency announced Tuesday that a database containing confidential medical information on scores of athletes, including prominent American competitors, has been breached by a Russian spy group.

WADA said a cyber espionage group operator called Tsar Team accessed the database by way of an Olympic account created for the Rio de Janeiro games last month.

After retrieving medical records it claimed were taken from the WADA system, the group posted some of the information online.

According to the records, the hackers said, American gold medal gymnast Simone Biles and tennis' Williams sisters have in the past tested positive for banned substances.

However, those uses were protected under "therapeutic use exemptions," which means an athlete can take any banned substance if there is a legitimate medical need for it.

USA Gymnastics statement regarding Simone Biles and WADA hack: pic.twitter.com/YTq2iVS7Vu

— USA Gymnastics (@USAGym) September 13, 2016

Biles responded on Twitter that the medication attributed to her was taken to treat attention deficit disorder (ADD).

"Please know, I believe in clean sport, have always followed the rules and will continue to do so," she said.

USA Gymnastics confirmed the breach of Biles' records in a statement Tuesday.

The data also showed that Serena and Venus Williams and Team USA basketball member Delle Donne had received certificates of approval to take otherwise banned substances.

"I'd like to thank the hackers for making the world aware that I legally take a prescription for a condition I've been diagnosed with, which WADA granted me an exception for," Donne said via Twitter. "Thanks guys!"

"WADA deeply regrets this situation and is very conscious of the threat that it represents to athletes whose confidential information has been divulged through this criminal act," Olivier Niggli, director general of the WADA, said in a statement. "We are reaching out to stakeholders ... regarding the specific athletes impacted."

"WADA has been informed by law enforcement authorities that these attacks are originating out of Russia," he continued. "These criminal acts are greatly compromising the effort by the global anti-doping community to re-establish trust in Russia."