The docking pilot boarded the Mexican naval ship, the Cuauhtémoc, shortly before the ship was to leave Pier 17 in the East River and head toward open sea. The pilot gave the command, and the ship, a tall sailing vessel with three masts, began to back away from the pier.

Once the Cuauhtémoc was clear of the slip, the docking pilot — whose job is to guide large ships from their berths to the harbor — gave a stop command. Then the pilot ordered the ship to proceed dead-slow-ahead — as slowly as possible, in a forward direction. Other commands followed, also ordering the ship forward, according to a federal report released Monday.

They seem to have had little effect. The ship instead continued to travel in the wrong direction, backward. And then it picked up speed, still traveling stern-first, before its masts slammed into the underside of the Brooklyn Bridge.

The crash on May 17 killed two crew members and injured 19 people. At the time of the crash, Mexican sailors were “manning the yards,” an old ritual in which sailors, high above deck, stand in rows along the horizontal spars on the masts.

The accident, captured on numerous cellphone videos, shocked the city: the sight of a huge sailing vessel colliding with the iconic bridge seemed almost like a disaster from another century.

The brief preliminary report released on Monday by the National Transportation Safety Board does not answer the central questions regarding the accident. It does not explain why the pilot’s orders had little effect, or shed light on the chain of events that left the ship traveling in the wrong direction. Nor does it explain how the vessel came to accelerate. It does not address whether there was a problem with the ship’s engines.