A U.S. citizen and private equity founder has been arrested in Moscow on Friday on suspicion of embezzlement.
According to Russian news agency IFAX, Michael Calvey, has been detained along with others in relation to the theft of 2.5 billion roubles ($37.5 million).
The same media has reported that Russian President Vladimir Putin is not aware of Calvey's detention and that the arrest was made based on evidence from The Federal Security Service of the Russian Federation (FSB).
Later Reuters reported that Calvey told a Russian court that the allegations were false and had arisen because his fund is in a dispute with Russia's Vostochny Bank.
In an earlier statement provided to CNBC Friday, the head of Russia's Sovereign Wealth Fund, Kirill Dmitriev, said he considered Calvey a professional.
"It is very difficult to comment on the situation around Michael Calvey's detention not knowing the details of the charges. However, here at the Russian Direct Investment Fund we know Michael Calvey and the team of Baring Vostok as highly professional investors, committed to the highest ethical standards accepted in the investment community" he said.
Speaking at the Munich Security Conference, Dmitriev added that he would personally vouch for Calvey.
"I am ready to provide personal guarantee for Michael Calvey and believe that he did a lot for attracting foreign investment in Russia and helped many Russian companies to grow and mature."
"We hope that it is a very transparent process that will follow," Dmitriev told CNBC's Hadley Gamble. "Mike said today he believes in the Russian legal system... so we need to make sure the system works, but we support Mike Calvey and we believe that hopefully this is a misunderstanding that gets resolved."
CNBC has learned that Dmitriev and Calvey have previously co-invested on a number of projects.