New York, New York - The deadly May collision of a Mexican Navy vessel with the Brooklyn Bridge resulted in over half a million dollars in damages to the sailing ship, US investigators said, without pinpointing a cause.

A preliminary report by the National Transportation Safety Board (NTSB) released Monday detailed the minute-by-minute movements of the Cuauhtemoc on May 17, when the training ship departed Manhattan on its way to Iceland.

After moving astern away from its docking location at Pier 17, a pilot on board the vessel directed it to go forward, the report said.

However, the ship began moving backwards up the East River, with its masts eventually colliding one by one with the Brooklyn Bridge.

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Numerous sailors were positioned among the Cuauhtemoc's rigging at the time of the crash, with two killed and nineteen others injured in chaotic scenes captured by onlookers.

The NTSB report said that alcohol and drug tests came back negative for the two pilots directing the Cuauhtemoc through the harbor, as well as the captain of a tugboat accompanying the ship.

The investigation "of all aspects of the accident is ongoing," the report said.

"We are examining the propulsion system, operating control system, relevant crew experience and training, and operating policies and procedures," it added.

New York authorities identified no significant damage to the bridge, according to the report.