Controversy erupted around curling yesterday when a Russian medal-winner failed a preliminary drug test and separately there were calls to bring in a video referee to the sport after a foul that went against Britain's women curlers.
The Russian athlete, believed to be Alexander Krushelnytsky, who won bronze in the mixed curling failed a preliminary drug test, putting his medal into jeopardy and throwing the spotlight on the decision to welcome 168 Russian athletes to Pyeongchang after the country was nominally banned for state-sponsored doping in Sochi four years ago.
He was found to have meldonium in his urine after playing in the mixed-curling tournament as a member of the Olympic Athletes from Russia team alongside his wife, Anastasia Bryzgalova.
The substance, which is used to treat heart attack victims, has been prohibited since 2016. It was commonly used by Russian athletes before that, including Maria Sharapova, who was banned for 15 months after she failed a test at the Australian Open in January 2016.
The International Olympic Committee said in a statement: "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."
According to the Russian newspaper Sport Express, Krushelnytsky's B sample will be opened today. If it is found to contain meldonium, he and his wife are likely to lose their medal.
Read more: Winter Olympics Day 10: Kiwis in action
The timing could not have been worst for Russia, who were hoping that their athletes would be able to march under their own flag at the closing ceremony next Sunday.
Meanwhile, Britain's women curlers were caught up in a bizarre controversy that led to calls for the introduction of video replays on Sunday, when they were penalised for a rare foul that cost them their Olympic match against Sweden even though television footage suggested the decision may have been incorrect.
Skip Eve Muirhead had taken the group-stage match to an extra end against unbeaten Sweden with the score all square at 6-6 and one stone remaining per team.
As she delivered Britain's final stone, the lights on the handle flashed red to indicate a foul had been committed.
The violation meant the stone was removed from play to leave Sweden a free shot at winning the match, which they took to claim an 8-6 victory.
The stone's red lights are programmed to flash if it is released after the hog line – the equivalent of a no-ball in cricket – or if the stone is touched twice.
However, replays appeared to show that neither had obviously occurred, with Muirhead releasing the stone in advance of the line.
Rugby and tennis have embraced video technology in recent years while football's FA Cup is trialling the Video Assistant Referee (VAR) this season. No such system exists in curling beyond the automated lights that measure the stone's release.
"I guess when you see the replays and it looks like all the ones before it, it is hard to take," said Muirhead, who guided her team to bronze at Sochi 2014.
"But it does come down I guess to inches and millimetres.
"It is the first stone I think I have hogged in my life and I guess when it comes at a time like that it is horrible.
"But it just makes it worse when you see it and it doesn't look like it is.
"We did get the stone tested and the stone is fine so there is nothing we can do. We have to move on."
Asked whether her hand had crossed the line she replied: "I don't know. If I did, I'd be out there telling them [the officials].
"When something like that happens, it makes it very tough to take and it's gutting it finished that way."
Glenn Howard, Team GB curling coach, said he was equally unsure what offence had been committed.
"I've only seen one replay and it looks like Eve has let go of the rock prior to the hog line and the light went off," he said.
"Then all they do is question the handle on the rock, and test whether the lights are working properly.
"The lights were working properly so therefore it becomes a hog line violation.
"The only thing I can think of is Eve has let go of the rock prior to the hog line, it crossed the line and then she happens to just touch it again with her finger on the handle to then activate the light. You could call it a double touch.
"It's a horrible way to finish the game."
Jackie Lockhart, who curled for Britain at four Olympics, said it was time for curling to investigate whether to follow the lead of other sports and bring video replays into the game.
"All sports are progressing and we probably have to start looking at video footage as well," she said on BBC.
"It is something they might have to look into."