Athletics' anti-doping watchdog is investigating claims that Russian officials tried to cover up a doping case involving high jumper Danil Lysenko.
Britain's Sunday Times reported on June 2 that officials from the Russian Athletics Federation (RUSAF) conspired to help Lysenko avoid a ban for failing to inform drug testers about his whereabouts last year.
The newspaper reported that Russian officials filed forged medical documents to the Athletics Integrity Unit (AIU), which investigates doping cases in the sport.
The documents came from fake doctors operating from a bogus clinic based in Moscow, the newspaper reported.
The case could scuttle Russia's efforts to end its suspension from international track and field in time for the 2020 Olympics in Japan.
The International Association of Athletics Federations (IAAF), the world ruling body for athletics, is due to rule next week on whether to maintain the ban.
The AIU said it was looking into "a matter relating to the explanation provided by a Russian athlete in defense of a whereabouts violation in 2018."
RUSAF said in a June 2 statement that it was cooperating with the AIU in its probe.
RUSAF has been suspended since a 2015 report commissioned by the World Anti-Doping Agency (WADA) found evidence of widespread doping in the sport.
Lysenko was one of the Russian athletes cleared to compete internationally by the IAAF. But he was provisionally suspended in August 2018 for missing doping tests.