The pilot of a helicopter that crashed Sunday into the East River in New York City, leaving five dead, has told police that one of the passengers' safety harnesses must have have somehow cut off the fuel supply, law-enforcement sources have told the New York Post.

But that scenario doesn't add up for one expert, who told the Post that the theory is “ 'highly implausible' since the lever, which is on the floor next to the pilot’s seat in that type of chopper, needs to be pulled up and back to be activated — and 'is normally fixed with a breakaway [safety] wire.' "

“I suspect a more plausible explanation is that the pilot simply activated the wrong lever, and this sometimes happens,” said aviation lawyer Gary C. Robb.

The National Transportation Safety Board is investigating the crash, but vice chairman Bella Dinh-Zarr said, "I have personally not seen this type of accident happen."

The helicopter was carrying five passengers and pilot Richard Vance when it plunged into the East River shortly after 7 a.m. on Sunday. The chopper quickly sank; one scenario says a safety pontoon on the helicopter for just such a water landing failed to inflate. Vance, 33, was the lone survivor.

The radio exchanges were frenetic, the Post wrote.

“Zero Lima Hotel, mayday, mayday!” Vance had radioed to air-traffic controllers at La Guardia Airport, referring to the Eurocopter AS350’s tail number, N350LH, just moments before the crash.

“Lima Hotel, you OK?” a controller replied.

“Engine failure!” Vance repeated multiple times as the controller struggled to hear him.

Vance, who has been flying for nine years, told police “he didn’t want to set [the chopper] down in Central Park, so he headed to the river,” the source said.

Footage of the crash was captured by a nearby witness.