At least five people were killed when a helicopter plunged into New York City's East River, authorities said on Monday.The pilot of the helicopter was the sole survivor of the crash that took place near Roosevelt Island on Sunday night, CNN quoted Fire Department New York (FDNY) Commissioner Daniel Nigro as saying on Monday.Two passengers died on the spot and three others succumbed to critical injuries in hospital, according to Nigro."One of the most difficult parts of the rescue was that five people were tightly harnessed," he said."People had to be cut out."In an audio recording of a Mayday call to LaGuardia Airport, the pilot, who was able to free himself and was later rescued, could be heard saying that the helicopter was experiencing engine failure.The Liberty Helicopters chopper had been chartered for a private photo shoot, the authorities said.Liberty Helicopters describes itself as "the largest and most experienced helicopter sightseeing and charter service in New York City", CNN reported.This is the company's third crash in 11 years, according to New York-based TV station WABC.In August 2009, nine people were killed when a helicopter and a small private plane collided over the Hudson river.Investigators said the helicopter was flying too high.Two years before that, in July 2007, a Liberty sightseeing chopper carrying eight people dropped into the Hudson river. An off-duty paramedic on board helped everyone escape, according to WABC.