According to an investigation board set up to examine the crash, the accident was almost certainly caused by a fault in the craft's power steering equipment.
Other possible causes have been excluded and this is currently the only theory, according to Hannu Melaranta of the investigation board.
However the company which manufactured the helicopter, Sikorsky, does not agree with the board’s verdict.
Meanwhile, the board has not been able to completely determine what happened during the accident.
Preparation of a final report on the accident will still take several months, reports the newspaper Helsingin Sanomat.
The Copterline craft crashed into the Gulf of Finland last August. Fourteen people died in the accident.