A helicopter crash victim is transferred by Fire Department officers at 34th Street Ferry Terminal in Manhattan of New York City, the United States, March 11, 2018. A helicopter crashed in New York City's East River on Sunday, killing at least two people, according to police. (Xinhua/Li Muzi)

NEW YORK, March 11 (Xinhua) -- A helicopter crashed into New York City's East River Sunday, killing at least two people.

Mayor Bill de Blasio has been briefed by the police and fire commissioners, according to Eric Phillips, the mayor's press secretary.

"At least one survivor, at least two fatalities," Phillips tweeted.

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

Witnesses told local media that the helicopter appeared to fill with water quickly.

"It's cold water. It was sinking really fast," Mary Lee, 66, told the New York Post. "By the time we got out here, we couldn't see it. It was under water."

The Federal Aviation Administration said a Eurocopter AS350 went down in the river near the northern end of Roosevelt Island at around 7:00 p.m. (2300 GMT) on Sunday. The cause of the crash is under investigation.

The local authorities have not yet confirmed the number of people on board and their condition. Some reports, quoting the U.S. Coast Guard, said there were six people aboard the private aircraft while others said there were five, quoting the New York Police Department.

Emergency responders including the police's special operations team were on the scene near East 90th Street, according to a twitter message from the police.

The skies over New York are 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 of the 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.