Sabotage is to blame for a string of recent failed doping tests for meldonium in Russia, the country's skating federation said Wednesday.

At least three Russian speed skaters have tested positive for meldonium, the same medicine found in Maria Sharapova's sample at the Australian Open.

"In our specific case, there is a very high probability, and we will prove it, that the banned substance was planted on three athletes deliberately," skating federation president Alexei Kravtsov said. "According to our information, it was done by their teammates."

Kravtsov did not name any suspects or say how the substance might have been given to them. He said the federation had tried to persuade police to investigate but had been turned down on the grounds that there was insufficient evidence that a crime had been committed.

Olympic short-track skating champion Semyon Yelistratov and reigning world sprint champion Pavel Kulizhnikov have failed doping tests for meldonium. Kravtsov later told Russian agency R-Sport that meldonium had also been found in a sample given by short-track skater Ekaterina Konstantinova.

Kravtsov said the federation had hired British lawyers to prove their innocence.

In separate cases, former European ice dancing champion Ekaterina Bobrova, volleyball player Alexander Markin and cyclist Eduard Vorganov are among Russian athletes who have reportedly tested positive for meldonium since it was banned Jan. 1.

The British Journal of Sports Medicine reported Wednesday that up to 490 athletes at the 2015 European Games in Baku were taking meldonium, when it was still legal.