CNN and ABC News, citing senior law enforcement officials they did not name, reported the pilot told investigators a passenger's bag may have inadvertently hit the emergency fuel shutoff button, leading to the crash.
The cause of the crash is unknown.
His father said he moved to New York City in October to work at Business Insider.
The skies over NY constantly buzz with helicopters carrying tourists, business people, traffic reporters, medical teams and others.
Carla Vallejos Blanco, a 29-year-old in town from Argentina, and Daniel Thompson, 34, and Tristan Hill, 29, were also among the dead.
Mayor's spokesman: At least 2 dead, 1 rescued from crashed helicopter in New York City's East River.
Video taken by a bystander showed the red helicopter descending slowly into the water, before listing on to its righthand side.
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"It took a while for the divers to get these people out", he said.
The passengers were reportedly trapped inside the submerged helicopter due to the safety harnesses they were wearing.
NYPD Commissioner James O'Neill said the helicopter, which had been privately chartered for a photo shoot, is owned by touring company Liberty Helicopters.
He said military pilots are usually trained in what's called a "helo dunker", in which pilots practice getting out of harnesses while submerged in water and flipped upside down.
Robb's statements align with what National Transportation Safety Board Vice Chair Bella Dinh-Zarr said during a press conference when asked about the pilot's theory.
Travis Howard, owner of the Retreat Gastropub in the Central West End, told The Washington Post his family had been in a panic since Sunday after learning a sightseeing helicopter plunged into the East River.
"It was sinking really fast", Mary Lee, 66, told the New York Post.
The official said it was not clear exactly when yellow inflatable pontoons on the helicopter began inflating and why they did not keep the helicopter afloat. "Screaming help and waving his arms like this", said Brianna Jesme and Celia Skvaril who witnessed the crash.
Vance headed to the river to avoid crashing on a crowded street, but was the only person aboard to escape before the chopper filled with water and sank. By the time we got out here, we couldn't see it.
A 16-member "Go Team" from the National Transportation Safety Board was headed to the scene this morning to investigate the cause of the crash.