NEW YORK, March 12 (Xinhua) -- A helicopter crashed into New York City's East River Sunday night and flipped upside down in the water, killing all five passengers aboard, police confirmed.

Lieutenant Thomas Antonetti with Public Information, New York Police Department (NYPD), confirmed the deaths to Xinhua early Monday morning when reached by phone.

The pilot of the helicopter, who managed to escape, was the only survivor.

At a press conference Sunday night, the Fire Department New York Commissioner Daniel Nigro said the five passengers became trapped in the overturned helicopter and had to be rescued from frigid waters by divers.

Three of them were taken to area hospitals in critical condition, while the other two were pronounced dead at the scene, he said.

The helicopter is owned by Liberty Helicopter Tours and was hired for a private photoshoot, New York Police Department Commissioner James O'Neill said.

Nigro said the harnesses designed to be worn for safety may have actually hindered the passengers' escape. First responders were not only operating in frigid water, but they were working against time inside a helicopter that by the time they arrived had turned upside down.

"The pilot freed himself, was taken by one of our fire boats ashore and was out on an ambulance," Nigro added.

The rescue operation Sunday took place in a 4 mph current in water about 50 feet (15 meters) deep, under challenging conditions.The helicopter was recovered in the rescue operation and towed to a pier.

The cause of the crash is unknown. The U.S. National Transportation Safety Board is investigating.

The Eurocopter AS350 went down in the waters between New York City's boroughs of Manhattan and Queens just after 7:00 p.m. local time (2300 GMT), according to the Federal Aviation Administration.

A video posted on Twitter shows a red helicopter landing hard in the water and then flipping on its side as its rotors beat the water.

Witnesses said the chopper appeared to quickly fill with water. Mary Lee, 66, told the New York Post she witnessed the crash from her apartment window.

"It's cold water. It was sinking really fast," Lee said. "By the time we got out here, we couldn't see it. It was under water."

The weather was calm at the time of the crash, with clear skies and winds at 16 to 19 km per hour, and a visibility of 16 km. The temperature of the East River was around 4 degrees Celsius.

The helicopter reported an engine failure during a mayday call to air traffic control, according to an audio posted to liveatc.net. The audio revealed that the helicopter was upside down in the water as rescue boats arrived at the scene.

The helicopter was owned by touring company Liberty Helicopters which describes itself on its website as "the largest and most experienced helicopter sightseeing and charter service in New York City."

The company has "a fleet of 10 state of the art Airbus Helicopters (formerly American Eurocopters)," according to the website. "We have been in business and flying safely for over 30 years," it says.

The skies over New York constantly buzz with helicopters carrying tourists, business people, traffic reporters, medical teams and others. Crashes are not uncommon.

In 2011, a helicopter carrying a veteran pilot and four tourists crashed into the East River, killing three tourists. In 2013, a helicopter pilot landed safely after the aircraft lost power at about 1,500 feet (457.2 meters) with four tourists on board. There were no serious injuries.