The former head of Russia's Anti-Doping Agency (RUSADA), a man at the center of a scandal over alleged state-sanctioned doping by Russian athletes and cover-ups by officials, has died unexpectedly just two months after resigning his post.

Former Executive Director Nikita Kamayev is the second disgraced former RUSADA executive to die in less than two weeks, as Russia scrambles to convince international officials to reverse a suspension that threatens to cripple Russia's participation at this year's Summer Olympics.

RUSADA said in a statement that the cause of death of the 52-year-old Kamayev was "presumably a massive heart attack."

Former RUSADA Director General Ramil Khabriev, another casualty of the doping accusations, said he had been "told" that Kamayev "was out cross-country skiing, came home, and felt pain in the area of the heart." (Some Russian media put Kamayev's age at 50.)

Kamayev and Khabriev both resigned in December from their positions at RUSADA, along with other senior officials in the agency, weeks after a special commission of the World Anti-Doping Agency (WADA) reported widespread, state-sponsored cheating and concealment.

As a result of that WADA commission's November report, Russian athletes have been temporarily suspended from international athletics.

Moscow has vowed to reform RUSADA and has been working to get the ban lifted in time for Russian track-and-field athletes to compete in the Summer Olympics in Rio de Janeiro in August.

Officials from the world governing body of athletics, the International Association of Athletics Federations (IAAF), which has also come under criticism in the scandal, continue work on their assessment of Russian anti-doping efforts ahead of the Rio games.

RUSADA also has confirmed that the agency's founding chairman, Vyacheslav Sinev, died on February 3. It did not elaborate on the cause of death for Sinev, who left RUSADA in 2010.

Following Sinev's departure from RUSADA in 2010, Kamayev took over as the day-to-day head of RUSADA from 2011 until his resignation in December.

Numerous Allegations

Kamayev rejected the WADA commission's findings of state-sponsored doping in Russia, saying the report was "politicized" and based on unreliable testimony from Russian athletes who had been caught doping.

He also rejected WADA accusations that agents from Russia's FSB security service infiltrated the drug-testing laboratory at the 2014 Winter Olympics in Sochi, saying those claims were the product of an "inflamed imagination."

The WADA commission's allegations were numerous, including the charge that RUSADA officers "routinely accept bribes from athletes," "provide advance notice of out-of-competition tests," and were part of a wider pattern of "direct intimidation and interference by the Russian state."

The independent commission said its evidence raised "major concerns" about the ability of RUSADA to function as an impartial institution.

It also reported the existence of an unaccredited shadow laboratory in Moscow with testing facilities that were identical to a WADA-accredited lab in the Russian capital.

The WADA report said the mysterious second facility -- called the Laboratory of the Moscow Committee of Sport for Identification for Prohibited Substances in Athlete Samples -- was controlled by Moscow's city government.

The commission also said it had evidence that the lab was "assisting in the cover-up of positive doping results by way of the destruction of samples."

RUSADA also was criticized by the WADA commission for not taking action against athletes who had been caught using performance-enhancing drugs.

Claims Of A Cover-Up

The head of WADA's independent commission, former WADA President Dick Pound, told reporters that the culture of doping by Russian athletes was "state-sponsored."

The report said that "it would be naive in the extreme to conclude that activities on the scale discovered could have occurred without the explicit or tacit approval of Russian governmental authorities."

Russian President Vladimir Putin rejected the complicity of his government, saying, "Responsibility should always be personal, if it is proved. Those who are guilty -- a coach, an organizer, an athlete -- they have to answer."

In December, WADA dispatched a team of independent experts to Russia to further investigate doping by Russian athletes and the allegations of a state-sponsored cover-up.

That team released a follow up report in January that alleged the corruption extended beyond Russia to include the leadership of the IAAF.

It also recommended a probe into the role of Russia's state-controlled VTB Bank as a sponsor of the IAAF under a 2007 deal, and a deal for the broadcasting rights for the 2013 IAAF World Championships in Moscow.

WADA officials said they suspect the fee for those rights was raised from about $6 million to $25 million in exchange for an agreement not to suspend Russian athletes who were caught doping.

On January 7, the IAAF Ethics Committee imposed lifetime bans from all athletics events against two Russian officials and the son of the former IAAF President Lamine Diack over multiple violations of anti-doping rules related to Russian marathon runner Lilya Shobukhova.

The ban -- imposed after the three were found to have blackmailed Shobukhova, targeted former All-Russia Athletics Federation (ARAF) head Valentin Balaknichev, former ARAF national team long-distance running coach Aleksei Melnikov, and former IAAF representative Papa Massata Diack of Senegal.

Senegal's government has said it will not take action on a request by France to extradite Massata Diack to face trial on charges of being part of an alleged "system of corruption."

With reporting by Reuters, AP, AFP, dpa, BBC, TASS, and Interfax

