The Spanish family killed when a New York sightseeing helicopter plunged into the Hudson River, leaving no survivors, were celebrating a birthday, a local official said Friday as divers scoured for wreckage.

A senior business executive, his wife and three children died along with the pilot when the helicopter malfunctioned, disintegrating in mid-air before plunging into the cold water.

The family were on a pleasure flight Thursday over Manhattan, described by the operator as the "ultimate sightseeing tour of New York City."

"They were celebrating the mom's 40th birthday with the tourist helicopter flight yesterday. The kids were all 11 years old and younger," said Jersey City mayor Steven Fulop.

A family member was flying in to recover their remains and officials were seeking to expedite the release of the bodies to be repatriated to Spain.

Police divers searched for parts of the helicopter that had yet to be recovered including the main rotor.

Fulop said working theories of the cause were a drone collision, a bird strike or mechanical failure.

'I heard a noise'

The crash has once again shone a light on US aviation safety in the wake of deadly incidents including the collision between a military helicopter and a passenger jet in Washington in January that claimed 67 lives.

A light aircraft crashed after departing Boca Raton airport in Florida on Friday, with local media reporting three people had been killed after the plane developed a mechanical issue.

There have been around 30 helicopter crashes in New York since 1980, Brooklyn Borough president Mark Levine told reporters, calling for tighter restrictions.

The cockpit of the passenger helicopter was lifted from the river by a barge crane overnight.

Swiss tourist Arafa Cherif, 47, told AFP "I heard a noise, but I thought it was a bomb or something."

"I was scared and so were the people next to me. Then I saw lots of police and firemen."

Police and fire service divers raced to the wreckage and rushed two of those rescued to hospital, but doctors were unable to save them.

Mayor Eric Adams said it was a "heartbreaking and tragic crash."

Video of the incident has emerged showing the cockpit apparently becoming detached from the rotor.

"It appears that the main rotor struck the body of the helicopter, cutting off the tail of the helicopter, which created an unrecoverable event," said former military aviator and attorney Jim Brauchle of Motley Rice.

"The two main causes of this phenomenon are mechanical failure or excessive maneuvering."