UPDATED 7:04 PM EDT -- Helicopter Crashes into Hudson River, Jersey City side

At least three people have been killed after a helicopter carrying two adults and three children from Spain crashed into the Jersey City side of the Hudson River on Thursday afternoon.

It was reported around 3:30 p.m. closer to the Jersey City side of the Hudson, right next to the air ventilation building for the Holland Tunnel, which goes underwater between Jersey City and lower Manhattan.

Officials said the five passengers on the helicopter were a mix of children and adults. The conditions of the other victims were said to be grave.

A witness told New York City media outlets that he saw the helicopter crash.

"I heard a loud snap ... I looked over ... and I could see a helicopter falling on its side and splash into the water," the witness said. "I didn't see anyone come out."

Another eye witness says he was jogging on the Manhattan side of the River and heard a loud "boom" and when he looked up, he saw the rotor seemed to have broken off the Helicopter and was in the air away from the body of the helicopter which was plummeting into the water.

The underside of inflatable pontoons can be seen floating above water, but the helicopter is upside down and underwater none the less.

New York City Police boats and Fire Boats responded along with North Hudson Regional Fire Department boats from New Jersey, and New Jersey State Police Boats.

The US Coast Guard has set up a safety zone perimeter around the crash site to keep the Hudson River Marine Traffic a safe distance away.

Video has emerged showing the final seconds of the helicopter as it plunged into the Hudson River.  At least FIVE SECTIONS of broken main rotor can also be seen plunging through the air into the water.   It looks like the main rotor of the aircraft failed and broke apart!

UPDATE 7:04 PM EDT --

It is now CONFIRMED; the main rotor of the helicopter DETACHED from the aircraft in-flight.   Whether that rotor struck something, like a large bird, became imbalanced and shook itself apart, is unknown.  The image below shows the broken-oiff main rotor blade, but much shorter than it should be: