A Moscow court has ordered Baring Vostok's founder Michael Calvey to be kept in custody until April 13.
The Basmanny court's judge, Artur Karpov, said on Saturday that Calvey, a U.S. citizen, was accused of a "serious crime" and could try to flee.
Baring Vostok is a major equity fund group in Russia. Its website says it has over $3.7 billion of committed capital.
Calvey, also a senior partner at the fund, set it up in 1994.
Earlier, Baring Vostok was cited by Interfax as saying that Calvey had been detained in connection to a dispute over Russia's Vostochny Bank, in which the fund is a controlling shareholder.
Before starting at Baring Vostok, Calvey worked for the European Bank for Reconstruction and Development and Salomon Brothers.