Soccer's world governing body has declared Russia's World Cup players free of doping but said it will continue to investigate other soccer players in the country.
In an investigation sparked by evidence provided by the World Anti-Doping Agency (WADA), FIFA said on May 22 that it has been examining the drug-testing samples of Russian players seized from Moscow's anti-doping laboratory along with information and data provided by the Moscow lab's former director turned whistle-blower Grigory Rodchenkov.
The soccer authority said it gave priority to reaching a conclusion on the players set to represent Russia at the World Cup tournament, which kicks off in Moscow on June 14. Russia last week named a provisional 28-man squad, plus seven reserves.
The Russian players have been subject to "several unannounced targeted doping controls" during the investigation, FIFA said in a statement.
"Insufficient evidence was found to assert an anti-doping rule violation. FIFA has informed the World Anti-Doping Agency of its conclusions, and WADA in turn has agreed with FIFA's decision to close the cases," it said.
The Russian Football Union's Acting President Aleksandr Alayev hailed the FIFA decision as "unbiased," "professional," and "just."
But a report this week by German public broadcaster ARD said WADA investigators remain "very suspicious" about possible doping in Russian soccer.
WADA's investigative reports on Russian doping have included documents suggesting Russia's soccer squad might have benefited from a system designed to hide positive doping tests during the 2014 World Cup. There was particular suspicion surrounding 34 cases identified by WADA.
Rodchenkov told the Associated Press news agency in February that he received government orders to prevent soccer players from being caught doping. He said there could still be sanctions from FIFA.
Rodchenkov, who now lives in hiding in the United States, told ARD that he received instructions to cover up doping in soccer from Russia's former Sports Minister Vitaly Mutko.
Mutko, who last year stepped down as chief organizer of the World Cup in Russia and resigned temporarily as head of the Russia's soccer federation, has categorically denied any doping in Russian soccer.
FIFA said that "investigations of several players unrelated to the FIFA World Cup are still ongoing and FIFA will continue to work on these cases in cooperation with WADA. Further updates will be provided in due course."
FIFA said it would not provide the names of individuals involved in its investigations.
FIFA said investigators have been conducting forensic checks on 154 urine samples of soccer players that were seized from the Moscow anti-doping lab to determine if there was any manipulation of the samples, including scratch marks which could prove that bottles were forced open and that tainted urine was swapped out.
A landmark report by WADA investigators in 2015 found that more than 1,000 Russian competitors were involved in a conspiracy to conceal positive drug tests over a five-year period. Soccer was among the sports involved.
WADA found widespread evidence of doping in Russia's track-and-field program, which has been banned from world competitions since 2015, as well as among athletes participating in the 2014 Winter Olympics in Sochi.
As a result of WADA's findings, Russia was banned from the Winter Olympics in South Korea in February, while hundreds of Russian athletes were barred from participating in the 2018 Winter Games and 2016 Summer Games in Rio de Janiero.