Recovery crews were searching on Friday for the scattered wreckage of a sightseeing helicopter that appeared to break apart over the Hudson River the previous day before slamming into the water, killing all six people on board.
Among the pieces that had not been found by Friday afternoon was the main rotor, according to Jennifer Homendy, the chair of the National Transportation Safety Board. Videos filmed by witnesses showed the part flying off the helicopter as it plunged into the river.
As she cautioned that the investigation was just beginning, Ms. Homendy would not speculate on what had caused the crash. A typical investigation can take a year or two to complete, according to the agency.
“Everything is on the table — we don’t rule anything out,” she said at a news conference with officials from Jersey City, near the site of the crash, on Friday afternoon. She did not offer a timetable for the investigation.
A team of 17 agents was on site to begin the painstaking process of reviewing the condition of the aircraft, a Bell 206L-4 helicopter. The fuselage was pulled from the water on Thursday. But in addition to the main rotor, other parts, including the tail rotor and the main transmission, were missing.
The aircraft had departed from a heliport in Lower Manhattan at about 2:50 p.m. on Thursday and crashed about 25 minutes later, Ms. Homendy said.
The crash killed Agustín Escobar, the chief executive for rail infrastructure for the technology company Siemens; his wife, Mercè Camprubí Montal; and their three children, all of whom were under 11. The family was on vacation from their home in Spain. The pilot, Seankese Johnson, a 36-year-old Navy veteran, also died in the crash.
Mr. Johnson’s flying record was still being reviewed, according to Ms. Homendy, who said he had accrued 788 total hours of flight time, and had a commercial pilot’s license.
Ms. Homendy, emphasizing that the investigation was in its very early stages, noted that the air-tour industry had been a concern for a number of years. She cited the March 2018 crash of a “doors-off” sightseeing helicopter that crashed into the East River after an accidental loss of engine power. Five passengers were killed in that crash, which led to a ban on doors-off helicopter flights in New York City.
She said that she was aware of reports of a large flock of birds near the area of the helicopter shortly before the crash, and that her team was looking into it.
Ms. Homendy asked members of the public to send in any videos or images they had of the crash, saying that footage circulating on social media was a help to investigators.
“A lot of those videos are from a very far distance, so we’ll have to look at those a little bit further back at headquarters,” she said. “But we are hoping to get additional videos that provide us information.”
