The medal-winning Russian curler Alexander Krushelnitsky has denied using banned drugs after testing positive for meldonium at the Winter Olympics as Russia announced a criminal investigation had been opened into the circumstances.

On Monday the court of arbitration for sport’s anti-doping division opened proceedings against Krushelnitsky, who won the mixed doubles bronze medal with his wife Anastasia Bryzgalova.

Krushelnitsky said: “First of all, I want to apologise to my partners on the Olympic team, our delegation and all the fans for not being able to protect ourselves from the problems that we faced today.

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“I’m very sorry that the historical victory of Russian curling has now become the subject of a doping scandal, which is doing immense harm to our sport and to all Russian sports in general. At the same time, I am ready to openly state that I have never, never during the time that I practice sport, used forbidden drugs and any other dishonest ways of competing.

“I am absolutely against doping and I have always tried to follow all anti-doping rules as closely as possible. My positive test for meldonium in this regard was for me and for Nastia not just a shock. This is a huge blow both to our reputation and career.”

The Olympic Athletes from Russia team said on Tuesday that “the circumstances of the case, do not provide any answers to the questions as to how and when meldonium could have gotten into the athlete’s body”.

For meldonium, which increases blood flow, to be performance-enhancing it must be used on a regular basis and over a prolonged period of time, the OAR statement added. The OAR said Krushelnitsky provided a clear drug sample on 22 January.

The statement added: “According to the unbiased results of laboratory analysis of Alexander Krushelnitsky’s samples detected concentration of the substance can be indicative of taking it once, which is not applied in medical practice and is absolutely useless and ineffective in the context of enhancing physical performance or sports results. No evidence of the systematic usage of meldonium is available in this particular case.

“Therefore the Russian Olympic Committee has initiated a comprehensive investigation of the circumstances which also includes the criminal investigation under the RF [Russian Federation] criminal law to establish the facts of the case in detail.”

Meldonium was found to be used by more than 100 Russian athletes in 2016. The former world No 1 Maria Sharapova served a 15-month ban for using the substance after it was added to the World Anti-Doping Agency’s prohibited list.

The positive test will ignite further debate about the involvement of Russian athletes at the Games. The ROC is under suspension by the International Olympic Committee following the systemic doping at the Sochi 2014 Olympics.

Play Video 0:50 IOC responds after Russian athlete charged with doping offence – video

The IOC in December determined that Russian athletes who proved they were clean would be allowed to compete as neutrals in the Games, in a team named the Olympic Athletes of Russia.

The OAR are competing under the Olympic flag and the Olympic anthem is being played at medal ceremonies in which they feature.

There are 168 athletes competing in the OAR team, who have so far won 11 medals, three silvers and eight bronzes – one of them won by Krushelnitsky and Bryzgalova in the first Olympic mixed doubles curling tournament.