The United States Embassy in Moscow has called on Russian authorities to allow its staff to visit a U.S. investment fund manager who has been jailed pending a fraud investigation.

Michael Calvey, founder and senior partner at the Baring Vostok equity firm, was detained last week and jailed for two months pending the investigation into suspected embezzlement. The arrest of a respected investment manager who has worked in Russia for 25 years has sent shockwaves through the Russian business community.

The U.S. Embassy said in a statement on Thursday that its staff has still not been able to visit Calvey seven days after he was detained despite multiple requests. The embassy said they expressed "strong concern" over the delay and "insist on access now."

Founder of the Baring Vostok investment fund Michael Calvey looks through a cage's class in the court room in Moscow, Russia, Saturday, Feb. 16, 2019. A Moscow court has ordered Baring Vostok's founder Michael Calvey to be kept in custody until April 13, 2019. (AP PhotoAlexander Zemlianichenko)

Founder of the Baring Vostok investment fund Michael Calvey looks through a cage's class in the court room in Moscow, Russia, Saturday, Feb. 16, 2019. A Moscow court has ordered Baring Vostok's founder Michael Calvey to be kept in custody until April 13, 2019. (AP PhotoAlexander Zemlianichenko)