More than 30 Russian athletes participating in Siberian Indoor Championships last weekend abruptly withdrew from competition when drug testers arrived at the event.
According to the Russian sports website Championat, as many as 36 athletes cited various illnesses for withdrawing from the competition at the city of Irkutsk.
Last month, Russian athletes were banned from competing under their nation's flag in the Winter Olympics that begin next month following allegations of a state-sponsored doping scheme involving athletes at the 2014 Games in Sochi.
In 2016, one Russian athlete tried to bribe a drug tester and another ran out of the stadium during her own race to avoid being tested, the World Anti-Doping Agency says.
As The Moscow Times notes, "Russia has a checkered history with the use of banned performance-enhancing drugs by its athletes, a legacy of the Soviet Union backed by historical evidence and testing records."
The Russian track and field federation "has started an internal investigation" into the incident, according to Championat.
Sergey Shubenkov, the 2015 world 110-meter hurdle champion, tweeted Wednesday that "Doping control drove in" and "a couple of dozen withdrew," according to a translation used by the BBC.
In a translation from Russia's state-run Tass news agency, Russian Athletics Federation President Dmitry Shlyakhtin said he wasn't surprised at the sudden exodus of would-be competitors.
"[We] have a lot of problems at the bottom [of athletics in Russia]," he said.
"Our suspicion that the doping situation hasn't improved in all regions has increased," he said, adding that without documentation, he could not be sure that the athletes who withdrew were using illegal drugs.