Media playback is unsupported on your device Media caption Investigators have begun examining the wreckage of the Bell 206 aircraft

A tourist killed when a helicopter crashed into a river in New York City, injuring three others, had been celebrating her birthday.

Sonia Marra, who died in the tragedy, had gone to the US to celebrate her 40th and see her family again for the first time in years, said a colleague.

Witnesses described how the aircraft spun out of control and fell into the East River near midtown Manhattan.

Investigators are trying to establish what caused Tuesday's crash.

The helicopter had been carrying a pilot and four passengers: Ms Marra, her parents and a friend.

Trapped

The trip to New York had been in celebration of the birthdays of Ms Marra and her stepfather, Paul Nicholson, 71.

Image caption Sonia Marra reportedly worked at a market in Sydney, Australia

He was aboard with his 60-year-old wife Harriet Nicholson - both are British citizens who live in Portugal.

They were joined by Ms Marra's friend, Helen Tamaki, 43, a New Zealand citizen who lives in Sydney, Australia.

The privately owned Bell 206 was flown by Paul Dudley, a friend of the family.

Ms Marra was recovered by rescue workers 90 minutes after the helicopter fell into the water near 34th Street. She was pronounced dead at the scene.

She was trapped inside the back of the aircraft as it sank about 50ft (15m) below the surface of the water, police said.

Cardiac arrest

Witnesses described a man in the water diving down and coming back up, possibly in an attempt to free a trapped passenger.

Mr Dudley was able to make his own way to the river bank and remained at the scene after Tuesday afternoon's tragedy.

Sunhe Dudley, the pilot's wife, told the Associated Press news agency: "These were actually very dear friends of ours that were in the helicopter."

Rescue officials said after the crash that two women - one of whom had suffered cardiac arrest - and a male passenger were admitted to hospitals.

Witnesses said the helicopter appeared outwardly intact when recovery workers pulled it out of the water.

'Splashed and sank'

Ms Marra had been employed at a fruit and vegetable market in the Sydney suburb of Glebe, said colleague Joe Galluzzo.

Media playback is unsupported on your device Media caption Eyewitness Joy Garnett said the helicopter was ''out of control from the moment it lifted''

The trip to New York had been a surprise gift from Ms Tamaki, Mr Galluzzo said, and Ms Marra had been excited about being reunited with her family, whom she had not seen in years.

Joy Garnett, a witness on a nearby dock, told AP the aircraft had risen about 25ft off the ground, before spinning two or three times and dropping into the water.

The helicopter flipped over, its blades sticking up out of the water, and was "obviously out of control", she said.

New York Mayor Michael Bloomberg said "a tragedy like this just breaks your heart", adding that the passengers had come "to see the best of our city".

The National Transportation Safety Board said the pilot had been interviewed as part of the investigation.