A MI-8 helicopter, carrying offshore oil rig workers, fell into the Black Sea on Monday 70 kilometers (45 miles) off Ukraine's coast after clipping the side of a drilling platform with its tail rotor.
The helicopter belonged to Ukraine's state-owned oil and gas company Naftogaz.
Ukraine's Transport and Communication Minister Yosyp Vinskyi told a news conference earlier in the day that the crash is believed to have been caused by pilot error.
"As far as I know, the helicopter was in good condition and had passed all regular check-ups," he said. "Therefore, the human factor may have been involved."
A special ministerial commission has been set up to investigate the cause of the crash.
The Mi-8, produced at the Mil Moscow Helicopter Plant, is a medium twin-turbine transport helicopter with 24 passenger capacity. It is the world's second most-produced helicopter, and is operated by over 50 countries.
