The allegations came to light after a helicopter crash left seven people died, including a presidential envoy and an environmental official. The group was part of a hunting trip to the mountainous area in Altai, south Siberia. Four people survived.
Authorities in Altai said the passengers were hunting goats and deer and had appropriate licenses, but photographs from the crash site posted on a local Internet site showed the carcasses of endangered mountain sheep, the argali.
"A criminal case into the illegal hunting of argali has been opened as part of the helicopter crash inquiry being carried out by the Investigation Committee," a source said.
Earlier on Monday, Russia's environmental regulator, Rosprirodnadzor, requested the Prosecutor General's Office open an inquiry into the high-profile hunting trip.
Earlier reports said the crash might have occurred, when the helicopter pilot descended to a minimum altitude either to pick up the carcass of a dead mountain goat, or to allow one of the party to take a better aim.
