OTTAWA, June 18 (Reuters) - The emergency flotation devices on a Canadian helicopter that crashed into the Atlantic Ocean in March did not activate, Canada's Transportation Safety Board said on Thursday. The accident killed 17 people.

The Sikorsky <UTX.N> S-92A helicopter hit the sea off the coast of Newfoundland after its tail rotor drive gears stopped working. The aircraft had been ferrying workers to two offshore oil facilities.

"The helicopter experienced significant forces during the impact with the water, and examination of the inflation bottles indicates that they had not released their compressed gas to inflate the flotation collars," the board said in a report.

"The reason the collars failed to inflate is still under investigation."

The helicopter sank about 40 miles (65 km) southeast of St. John's, capital of the province of Newfoundland and Labrador. It had been heading for the Sea Rose production vessel at Husky Energy Inc's <HSE.TO> White Rose oil field and the Hibernia oil platform.

Hibernia is owned by Petro-Canada <PCA.TO>, Exxon Mobil Corp <XOM.N>, Chevron Corp <CVX.N>, Murphy Oil Corp <MUR.N>, Norway's StatoilHydro <STL.OL> and the government of Canada.

One person survived the crash, the worst in Canada since a Swissair passenger jet slammed into the Atlantic off the coast of Nova Scotia in September 1998, killing 229 people. (Reporting by David Ljunggren; editing by Peter Galloway)

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