The Mexican navy tall ship that smashed into the Brooklyn Bridge in May was inexplicably sailing backwards — and picked up speed — before the fatal collision, according to officials.

The preliminary report released Monday by the National Transportation Safety Board (NTSB) leaves more questions than answers on the crash that killed two crew members and left 19 other people injured, including why the docking pilot’s orders to stop the vessel didn’t have any effect.

A tugboat was trying to assist the doomed Cuauhtémoc, which had hundreds of Mexican naval cadets on board, when the crew seemingly lost control of the vessel.

A tugboat was trying to assist the doomed Cuauhtémoc, which had hundreds of Mexican naval cadets on board, when the crew seemingly lost control of the vessel.

“The upper sections of all three masts of the Cuauhtémoc contacted the underside of the Brooklyn Bridge, one by one,” the report states.

The estimated damage to the 147-foot-tall training vessel is expected to exceed $500,000.

The initial report makes no mention of mechanical failures that hindered steering capabilities, as insiders close to the case initially reported.

The 43-year-old vessel was on its way to the Brooklyn waterfront to refuel before setting sail for Iceland when the “major marine casualty” occurred.

The stop in Lower Manhattan was the fourth in an eight-month, 22-stop voyage around the globe to train the class of naval cadets.

After four days in port at Pier 17 in South Street Seaport, a sea pilot boarded the Cuauhtémoc and a local docking pilot arrived to guide the vessel safely out of the pier. Weather conditions were smooth and visibility was clear, the report said. 

The docking pilot gave directions for the Cuauhtémoc to move its rear, “which were acknowledged by the captain, translated to Spanish, and relayed to another crewmember on the deck below,” the NTSB stated.

The vessel began to back out of Pier 17 and the Charles D. McAllister, a tugboat, was ordered to reposition the ship so that it would be facing the direction of travel.

“Once clear of the slip, the docking pilot gave a stop command, gave a dead-slow-ahead order” and ordered the McAllister to push the right side of the Cuauhtémoc so that its rear was facing the Brooklyn Bridge.

But instead of going forward as ordered, the navy ship moved backwards — suddenly picking up speed from 3.3 knots (3.8 mph) to 5.9 knots (6.8 mph) and slamming into the iconic, heavily trafficked bridge as horrified witnesses watched.

At the time, dozens of cadets were “manning the masts,” meaning they were standing on and strapped to the ship’s three masts — a universal sign of respect every time a ship enters and leaves a port.

Two crew members who were on the masts plummeted to the ship’s deck during the collision and were later pronounced dead at local hospitals.

The vessel also hit a seawall on the Brooklyn side of the East River before the crew deployed both anchors.

The Brooklyn Bridge didn’t sustain any structural damage, though some loss of paint was observed, the report states.

Both pilots and the captain from the tugboat tested negative for alcohol and other drugs.

The report doesn’t explain why the pilot’s orders to move forward weren’t followed, or why the Cuauhtémoc picked up speed before the tragic collision.

In late May, the commander of the Mexican Navy, Adm. Raymundo Pedro Morales Ángeles, seemed to put some blame on the dock pilot who was advising the captain on how to navigate out of the channel.

“All the maneuvering that the ship did, from the moment it leaves the dock until it collided, is under the control of the pilot. Who decides how the maneuver is performed? The port pilot, precisely,” AMorales Ángeles told reporters at a news conference. He later backpedaled, saying it was too early to speculate whether the pilot was responsible.

It could be another year or so before the final report on the crash is released, providing clear answers to the lingering mystery.

“The preliminary report, released yesterday, stated NTSB investigators have been on board the vessel for a preliminary examination. The NTSB investigation of all aspects of the accident is ongoing; we are examining the propulsion system, operating control system, relevant crew experience and training, and operating policies and procedures,” a spokesperson for the agency told The Post.

The Mexican Navy is conducting its own investigation, with President Claudia Sheinbaum stating it would explore whether a mechanical failure, the tugboat or human error could be to blame.