A helicopter crashed in Russia's Far Esttern Amur region, the Investigative Committee said on Friday.
The committee said in a statement that there were three passengers and a pilot on board the Robinson R-66 helicopter, and their fate is unknown at the moment.
"During the search and rescue operations, the location of the aircraft that crashed in the Amur region was established. Information on the number of victims is being clarified," it said.
The investigators opened a criminal case on violations in the operation of air transport.
The cause of the crash is being established, the committee said, adding that the incident occurred on Thursday.
