A female passenger was killed and three others seriously hurt when the chopper went down. Sonia Marra, 40, was pulled from the water about 90 minutes after the helicopter went down at about 3:22 p.m. She was pronounced dead at the scene.
According to Mark Rosekind, a member of the NTSB, the privately operated Bell 206 likely did not have a flight data recorder, or "black box."
Investigators are hoping the engine monitors and Global Positioning System navigation equipment will provide clues into the cause of the crash.
Experts are also looking at weather played a factor in the crash. The weather was clear but a little windy, with winds of 10 mph gusting to 20 mph and visibility of 10 miles, according to the weather station at LaGuardia airport.
Winds can sometimes be rougher along the river because of turbulence caused by tall buildings and bridges.
A piece of one of the chopper's main rotor blades was missing, but it's unclear whether it broke before or after the crash.
The pilot, Paul Dudley, had more than 2,200 hours of flight experience, including 500 hours in Bell 206s.
The Associated Press contributed to this report.
