The roster of the youth hockey team vanished from its website Wednesday, a day before the players were to fly to Grand Forks, N.D., for the world championships, and it was announced that the under-17 team would replace the under-18 squad at the tournament, which begins April 14.

The abrupt change of the entire squad was immediately linked by the Russian news media to meldonium.

The day before the team was pulled, a closely followed Russian site, Allhockey.ru, reported that many players had tested positive for meldonium and that the team would have to be replaced. On Wednesday, the team’s coaches declined to comment on whether the change was connected to the drug, but many Russian observers could not see what else could have led to such a wholesale move.

“Meldonium Has Rejuvenated Russian Hockey,” the website Gazeta.ru noted wryly in a headline.

Also this week, the national men’s curling team was switched out the day before the world championships began in Switzerland. Days earlier, a men’s professional volleyball team, Gazprom-Yugra, said it would not be fielding three of its top players at the European championships. In both cases, the teams’ coaches said the substitutions had nothing to do with meldonium.

Dmitri Svitsev, head of Russia’s curling federation, told the leading Russian sports newspaper R-Sport: “Our athletes have not taken that drug for a long time. The changes in the team were based on a training decision and not problems with doping.”

Meldonium was given openly to Russian athletes for decades, and many trainers have insisted that it does not enhance performance. Sold as Mildronate, meldonium is not approved for sale in the United States or the European Union, but is sold over the counter in Russia and some Eastern European countries. A study by a Russian antidoping center found that more than 700 Russian athletes were on meldonium last year before the ban, according to the Russian newspaper RBK.

New questions are being raised, however, as to whether some athletes may fail drug tests even without having taken meldonium after it was banned.