A Russian bronze medalist has reportedly left the Olympic village and surrendered his accreditation after failing a drug test at the Pyeongchang Winter Games in South Korea.

Curler Alexander Krushelnitsky, who won bronze with his wife in mixed doubles last week, is suspected of testing positive for the banned substance meldonium, a source at the Games told Reuters news agency on Sunday.

The Court of Arbitration for Sport (CAS) opened a case against the Russian athlete after a request from the International Olympic Committee (IOC).

Krushelnitsky is awaiting the results of a second sample, which will determine whether he used the substance that increases blood flow and improves exercise capacity in athletes.

Krushelnitsky's name was not officially revealed, but Reuters said it confirmed the athlete's name with a spokesman from the Russian Olympic delegation.

The IOC said in a statement that "on the one hand it is extremely disappointing when prohibited substances might have been used, but on the other hand it shows the effectiveness of the anti‑doping system at the Games which protects the rights of all the clean athletes".

The case may prevent the Russian athletes from using their national flag during Sunday's closing ceremony.

Nearly 170 Russian athletes are competing as part of the Olympic Athletes from Russia (OAR) team after their country was banned from the Pyeongchang Games following claims of state-sponsored doping during the 2014 Sochi Olympics.

Meldonium was banned in January 2016, when a large number of Russian athletes, including tennis player Maria Sharapova, was found to be using the drug to enhance their performance. As a result, Sharapova was handed a 15-month suspension.

Bans overturned

Earlier this month, CAS overturned the bans of more than two dozen Russian athletes after it "unanimously found" that the evidence presented was "insufficient to establish" that doping rules were violated.

The decision "annulled" the sanctions imposed against the athletes and their individual medal results in the 2014 Sochi Winter Games were "reinstated".

The IOC president called the decision as an "unprecedented attack on the integrity of the Olympic Games and sport".

In 2016, a report by the World Anti-Doping Agency (WADA) found that more than 1,000 Russian athletes were involved in or benefited from a state-sponsored plan to hide positive doping tests.

According to WADA, the cover-up dated back to at least 2011. Athletes competing at the 2012 Olympics, 2013 world athletics championships and 2014 Winter Olympics in Sochi were involved.

The athletes competed in more than 30 sports, including football, the report found.

At the time, WADA called on the IOC to bar Russia from participating in the 2016 Summer Olympics in Brazil.

The country's track and field team were banned from participating in Rio de Janeiro, and the entire Russian Paralympic team was also banned from the 2016 Paralympic Games.