(AP) - A small plane collided with a sightseeinghelicopter carrying Italian tourists over the Hudson River onSaturday, scattering debris in the water and forcing people on theNew Jersey waterfront to scamper for cover. Authorities believe allnine people aboard the two aircraft were killed.

Another helicopter pilot on the ground at the heliport forLiberty Tours, which operated the doomed sightseeing craft, saw theplane approaching the helicopter and tried to radio an alert to thepilots, police Commissioner Raymond Kelly said. The warning wasn'theard or didn't happen in time.

The collision, which Mayor Michael Bloomberg said was "notsurvivable," happened just after noon and was seen by thousands ofpeople enjoying a crystal-clear summer day from the New York andNew Jersey sides of the river.

"First I saw a piece of something flying through the air. ThenI saw the helicopter going down into the water," said Kelly Owen,a Florida tourist at a Manhattan park. "I thought it was myimagination."

The two aircraft went down just south of the stretch of riverwhere a US Airways jet landed safely seven months ago. But thistime, there was no miracle.

"This is not going to have a happy ending," Bloomberg said.Hours after the collision, he said he thought it fair to say "thishas changed from a rescue to a recovery mission."

The National Transportation Safety Board was investigating thecause of the collision.

Two bodies were recovered in the water, one floating free andone in the wreckage, and other bodies were spotted in the debris inthe river, the mayor said. The crash victims included five Italiantourists and a pilot on the helicopter and the three people on theplane, including a child, Bloomberg said.

Witnesses described seeing a low-flying plane smashing into thehelicopter, and then wreckage scattering. One of the plane's wingswas severed by the impact.

The plane, headed for Ocean City, N.J., left Teterboro Airportin New Jersey at 11:54 a.m., the Port Authority of New York and NewJersey said in a statement. It had landed at the airport 25 minutesearlier with the pilot aboard to pick up two passengers.

The plane had started its journey in Pennsylvania, an officialfamiliar with the plane's flight path told The Associated Press oncondition of anonymity because he wasn't authorized to speakpublicly.

Post photos of Hudson chopper crash in MyPics on News12.com.