The pilot said one of the passenger's bags may have inadvertently hit the emergency fuel shutoff button, leading to the crash that killed five passengers, a senior law enforcement official said.
A police source identified the pilot as 33-year-old Richard Vance.
The passengers were on a Liberty Helicopters chopper that had been chartered for a private photo shoot, authorities said. All the victims were between 26 and 34 years old, according to the New York Police Department.
The helicopter was lifted from the water on Monday afternoon and is being examined by experts from the National Transportation Safety Board, NTSB member Bella Dinh-Zarr said.
Investigators will inspect the helicopter, its flotation devices, the weather and other factors in their attempt to determine the cause of the crash, she said.
The crash was the third for Liberty Helicopters in the past 11 years. US Sen. Chuck Schumer of New York called on the FAA to suspend Liberty Helicopters' FAA operating certificate until the company's safety record and this crash are fully assessed.
"Three (crashes) is too many," Schumer said. "There are too many allegations. No one knows what's happened. I don't think Liberty should be flying until we get to the bottom of this."
Chopper was upside down and submerged
The Federal Aviation Administration
said the helicopter, a Eurocopter AS350, went down in the East River near Roosevelt Island at 7 p.m.
In an audio recording of a mayday call to LaGuardia Airport, the pilot said the helicopter was experiencing engine failure.
When emergency workers responded, the helicopter was upside down and submerged, authorities said. Police called for a barge with a crane to pull the chopper out of the water near 23rd Street.
"One of the most difficult parts of the rescue were that five people were tightly harnessed," Fire Department of New York Commissioner Daniel Nigro said. "People had to be cut out."
The pilot was able to free himself and was rescued, Nigro said.
Passengers are identified
Richard Vance, the pilot in Sunday's crash, is a licensed helicopter pilot from Danbury, Connecticut, FAA records show. His current commercial pilot license was issued in September 2011, according to FAA records.
Anthony Vance, the pilot's brother, told CNN in a phone interview that "he did his job and got out alive."
"He's a true f---ing pilot, so just let him be," he said.
The NYPD identified the victims as Carla Vallejos Blanco, 29; Daniel Thompson, 34; Tristian Hill, 29; Trevor Cadigan, 26; and Brian McDaniel, 26.
Vallejos Blanco, a tourist from Argentina, was on a vacation taking a photographic tour of the city when she was killed, according to deputy consul general Eduardo Almirantearena. The consulate said her family is working with the New York City medical examiner to bring her body back to Argentina.
Cuenca del Plata University in Argentina said she studied art, design and communications.
Cadigan was an intern at media organization Business Insider until a few weeks ago, according to a company spokesman.
"He was a smart, talented, and ambitious young journalist and producer who was well-liked and made a big contribution. Our hearts go out to his family and friends," the company said.
Cadigan was the son of Jerry Cadigan, the production manager for WFAA in Dallas, and had interned at WFAA previously.
"The entire WFAA family is heartbroken by the sudden and tragic loss of Trevor Cadigan," Brad Ramsey, WFAA president and general manager, said in a statement. "We would like to thank the many friends and former employees of WFAA who have reached out to offer your condolences and support. Our thoughts and prayers are with all of Trevor's family and friends, and with the families of all of the victims of yesterday's tragic accident."
McDaniel was a fire rescue officer for Dallas Fire-Rescue who had been hired in May 2016, the department said in a statement.
"Despite his short tenure, hearts are heavy with grief as we not only try to come to grips with his loss departmentally; but to also be there in every way that we can for his family."
Company had 3 crashes in 11 years
Liberty Helicopters describes itself
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 Eurocopter)," according to the website. "We have been in business and flying safely for over 30 years," the website says.
This is the company's third crash
since 2007. In August 2009, nine people were killed after a helicopter and a small, private plane crashed into each other over the Hudson River. The FAA said the helicopter and small plane were communicating on different radio frequencies "and were not aware of each other's positions."
Two years before that, in July 2007, a Liberty sightseeing chopper carrying eight people suffered a rotor blade separation
midflight and crashed into the Hudson River.
All passengers were wearing inflatable life vests, and the pilot said she deployed pop-out floats, the National Transportation Safety Board said. Neither the pilot nor the seven passengers were seriously injured.
In all, the FAA has documented 16 accidents or incidents involving Liberty Helicopters since 1995. The 2009 crash was the only previous incident with fatalities.
There are no accident or incident histories or closed enforcement actions for the Eurocopter AS350 helicopter, the N350LH, or for pilot Richard Vance, according to FAA spokesman Jim Peters.
The NTSB will likely look at three things: the pilot's training, experience and immediate response during the crash; what, if anything, on the helicopter caused the crash; and what environmental factors may have contributed to the crash, said Gary C. Robb, an aviation attorney based in Missouri.
Robb said the NTSB would then release a preliminary report, and a probable-cause accident report would follow detailing what happened during the crash.
He said that any helicopter operating around water should have floats so it can land on water and stay upright. Based on the video of the crash, Robb speculated that one of the floats on the helicopter did not activate, which may have caused it to turn sideways in the water.
Liberty Helicopters posted a statement on its website, saying it is "focused on supporting the families affected by this tragic accident and on fully cooperating with the FAA and NTSB investigations." It said it was referring all press inquiries to federal agencies.