A helicopter that crashed in New York City's East River with five people onboard had been in the shop just two days before the fatal flight, accident investigators said in a report released Wednesday.

Mechanics had just wrapped up their annual inspection of the Bell 206 helicopter on Oct. 2, the National Transportation Safety Board said in the preliminary report.

During an annual inspection mechanics take much of an aircraft apart and put it together again. The work can take several weeks.

Pilot Paul Dudley told the NTSB he had just taken off from the East 34th Street Heliport and was 30 to 50 feet above the river when the nose of the helicopter swung unexpectedly to the left.

When he tried to turn right to return to the heliport, the aircraft went out of control, Dudley told investigators.

Three-fourths of one main rotor blade broke off when the helicopter hit the water, the report said.

Investigators had previously said they were unsure if the blade broke before or after the impact. They have not found the missing piece, according to the report.