"The RUSADA former executive director died suddenly at the age of 52," RUSADA said in a statement. "The cause is presumed to be a massive heart attack."
"It is a great loss and unexpected for us," the Russian anti-doping agency's interim general director Anna Antseliovich, who took charge after the scandal, told R-Sport news agency.
Kamayev, who resigned as RUSADA's executive director in December, died after feeling ill while skiing, the former general director of the anti-doping agency, Ramil Khabriyev told TASS news agency earlier today.
Kamayev had resigned along with three other RUSADA top officials after a report by a World Anti-Doping Agency (WADA) independent commission accused Russia of routine violations of testing standards and allowing suspended athletes to compete.
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The officials resigned after President Vladimir Putin called for Russian officials, trainers and athletes to take responsibility for engaging in or abetting doping.
Both RUSADA and Moscow's anti-doping laboratory were suspended over the bombshell report.
RUSADA in its statement praised Kamayev as "an experienced and understanding manager" who "managed to create a friendly atmosphere among staff".
"We greatly regret his death," he added.
Kamayev had initially responded defiantly to the WADA report released in November, branding the suspension of Moscow's anti-doping laboratory "utter nonsense" and ridiculing the allegations as reminiscent of "the epoch of James Bond."
"I have a holster, a pistol, and every day I go to the basements of Lubyanka," he scoffed to journalists in November, using the informal name for the KGB/FSB security service headquarters building in central Moscow.