A sightseeing helicopter with five Italian tourists on board collided with a light aircraft over New York's Hudson River on Saturday, sending wreckage from both plunging into the waters.
All nine people on board the two aircraft were assumed dead, Mayor Michael Bloomberg said in broadcast remarks.
"It appears that this was not survivable," Bloomberg said. "This has changed from a rescue to a recovery mission."
Two bodies had been recovered, including one that had floated free, and several bodies were in the submerged wreckage of one of the craft that had been spotted.
Bloomberg said that because of the disfigurement through the crash, it was not clear if it was the helicopter or the 1976 single-engine Piper.
"There is some evidence from eyewitnesses that one of the wings of the airplane was ... possibly severed by the rotors of the helicopter," Bloomberg said.
Divers were searching in the murky 10 metre-depths of the swift-flowing Hudson River for other bodies and the second wreckage, Bloomberg said.
The mayor said special community affairs officials had been sent to help the families of the Italian tourists.
"I gather they don't speak English," he said, adding the officials would "help the families get through this difficult period."
The helicopter operated by Liberty Tours had taken off from the 30th Street helipad for a sightseeing tour about noon, CNN reported.
The single-engine aircraft, carrying three people including one child, had taken off from Teterboro Airport outside New York City and was headed south to the New Jersey beach town of Ocean City.
Bloomberg noted that small aircraft and helicopters have flight corridors over the Hudson and East Rivers. While there is no legal requirement for radio contact and visual flight rules were in effect, he said it was common practice for pilots to use a radio frequency identified on all maps to make each other aware of their positions.
"It is a crowded busy area, and pilots who fly there are well trained and have practice," he said.
It was not clear if the pilots were in radio contact with each other.