NEW YORK -- Federal investigators said they would examine photos taken in the moments before ainto New York's East River by the five passengers who died. The National Transportation Safety Board also said it would look at the switch and the chopper's flotation devices to figure out what caused Sunday's crash.
Thewere part of an aerial photography tour, and the pilot was the only survivor.
The pilot told police a tether from a passenger's safety harness wrapped around the helicopter's fuel shut-off lever, CBS News transportation correspondent Kris Van Cleave reports. It's located on the floor of the helicopter near some of the flight controls.
That accidentally cut off the fuel supply, the pilot said.
NTSB member Bella Dinh-Zarr said the agency hasn't spoken to the pilot but hopes to do so.
"Mayday, mayday, mayday," pilot Richard Vance said in an emergency radio call as the Eurocopter AS350 tour helicopter foundered. "East River - engine failure."
The chopper flipped over and quickly sank, killing a Texas firefighter, an Argentine woman, a young video journalist, a former basketball team assistant and another person on what authorities said was a charter flight to take photos.
The helicopter's six emergency floats inflated, but Dinh-Zarr said investigators would look at whether there were any problems with those devices or the harnesses available to passengers on a chopper that was legally allowed to fly with its doors open. The NTSB and other agencies involved in the probe also hope to recover the passengers' cameras and electronics "to capture a digital portrait of the last moments of this flight," she said.
No one answered an email Monday to Vance, a 33-year-old licensed commercial pilot for seven years who's also licensed as a flight instructor. A possible phone number for him in Danbury, Connecticut, wasn't working.
A floating crane slowly raised the submerged helicopter to the surface Monday and towed it off to be examined, as Democratic U.S. Sen. Chuck Schumer said federal regulators should suspend flights by the helicopter's owner until the facts of the crash are known.
The owner, Liberty Helicopters, referred all inquiries to federal authorities. The Federal Aviation Administration said it was investigating whether the flight had met regulations.
Liberty, a tour and charter helicopter company, has been involved in at least five accidents or other incidents in the last 10 years, according to FAA data. Three incidents ended in safe landings after, for example, one chopper clipped another while taking off from a helipad. But an August 2009 collision over the Hudson River between a Liberty chopper and a small private plane killed nine people, including a group of Italian tourists.
The company paid $23,576 in fines in 2010 and 2011 for violating maintenance, record-keeping and flight operations rules, the FAA said. Three subsequent maintenance violations in 2011 and 2012 didn't result in any fines.
Witnesses to Sunday's crash said the helicopter was flying noisily, then suddenly dropped and quickly submerged. A bystander's video showed the helicopter land hard and then capsize in water about 50 feet deep.
Emergency divers had to get the passengers out of tight safety harnesses while they were upside down, fire department Commissioner Daniel Nigro said. Vance freed himself.
The passengers who died included Dallas fire Officer Brian McDaniel, 26, and his high school friend Trevor Cadigan, 26, a journalist who hailed from Dallas but had recently moved to New York.
McDaniel had been with the Dallas Fire-Rescue Department since May 2016.
"He decided he wanted to help people" and set out to do it, said Cole Collins, a childhood friend from Dallas. "He didn't care about being a flashy person or making a lot of money. He loved his family and friends and this city."
McDaniel was visiting Cadigan, who had recently finished an internship at the Business Insider news site.
"He was a smart, talented, and ambitious young journalist and producer who was well-liked and made a big contribution," Business Insider said in a statement.
A 2016 graduate of Southern Methodist University, Cadigan had previously freelanced with an entertainment and culture site managed by the Dallas Morning News and interned with his hometown's WFAA-TV. His father is the station's production manager.
Megan Polakoff, who went to high school with Cadigan and McDaniel, told CBS Dallas-Fort Worth station KTVT-TV that they were close.
"They were just funny," she told the station. "It was like they would just feed off each other's humor."
Polakoff kept in touch with McDaniel. No matter the circumstances, she said, he always welcomed her warmly.
"I just always remember him with a smile and his bear hugs," she said. "He would just give the biggest hugs."
Carla Vallejos Blanco, 29, was a tourist from Corrientes, Argentina, who'd been in New York for a few days, said her country's consul in New York, Mateo Estreme.
Tristan Hill, 29 and engaged to be married, was most recently working at a sightseeing tour company but had previously been a basketball operations assistant with the Westchester Knicks, a Development League affiliate of the New York Knicks.
He "brightened every room he entered, with a contagious smile and an unparalleled enthusiasm for life," the team said in a statement.
The fifth victim was Daniel Thompson, 34, police said.