A trainer for a champion figure skater, Ekaterina Bobrova, said her results were “three or four times less.” Nadezhda Kotlyarova, a track sprinter, told the news agency TASS her sample showed only 0.025 of a microgram. Russia’s volleyball federation said Alexander Markin’s positive test contained 0.3 of a microgram, and Russia’s swimming federation said it had sent a formal appeal to its international body showing that results for Yulia Efimova — a bronze medal winner at the 2012 London Games — were also below the limit.

It was unclear how many Russian athletes would be able to prove they had taken the drug before it was outlawed. Most of the suspended Russians tested positive in late February or early March and have not released the precise results of their tests. Bobrova’s trainer, Alexander Zhulin, said she had stopped taking meldonium between September and November.

Sharapova, who is provisionally suspended by the International Tennis Federation, tested positive at the Australian Open in January and said she did not know meldonium, which she had been taking for 10 years, had been added to the prohibited list. She said she did not open a link in an email sent in December explaining the changes to the list for 2016.

“Given the fact that scores of athletes have tested positive for taking what previously was a legal product, it’s clear WADA did not handle this properly last year and they’re trying to make up for it now,” Sharapova’s lawyer, John Haggerty, said in a statement. “The notice underscores why so many legitimate questions have been raised concerning WADA’s process in banning meldonium as well as the manner in which they notified players.”

National antidoping agencies and sport federations were informed of the meldonium ban three months before it took effect, to give athletes time to allow the drug to clear their systems or to apply for an exemption.

Nichols, the WADA spokesman, said that it had not been a mistake to ban the drug without precise information on how long it stayed in the body. He added that all sides had time to express their concerns during a yearlong monitoring of the drug in 2015.