UPDATE 5:34PM EST: A woman was killed Tuesday when the chopper she and four others were riding in went out of control and crashed into the East River.

It took more than an hour to find the unidentified woman in the murky water, police said.

Pilot Paul Dudley and three of the other passengers were plucked from the rough water shortly after the Bell 206 chopper went down around 3 p.m. and quickly submerged.

The chopper had taken off from the E. 34th St. helipad for what was supposed to be a private tour of the city when something went wrong, police said.

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Witnesses said the helicopter had gotten about 30 feet off the ground when it stopped climbing and started making a curlicue.

The commercial helicopter went down in about 50 feet of water, but within minutes police divers were able to locate three survivors and drag them to shore.

None of them appeared to be wearing life preservers.

Dudley, a veteran chopper pilot who has homes in both New York and New Jersey, apparently made it back to shore on his own, police said.

UPDATE 4:47PM EST: [NBC NEWS REPORTS] A helicopter carrying a pilot and four tourists crashed in the East River shortly after taking off Tuesday, and three of the passengers were in critical condition.

NYPD spokesman Paul Browne said the helicopter had just taken off from the 34th Street heliport and was trying to return after unknown issues in the air.

Authorities said the pilot and three tourists, who were from England, were pulled out of the water shortly after the crash, and the fourth tourist was found about another hour later after an extensive underwater search.

NBC New York has learned that the pilot, Paul Dudley, is the same pilot who safely landed a Cessna 172 in Calvert Vaux Park near Coney Island in November 2006. In that case, the plane’s engine failed and Dudley was forced to make an emergency landing.

The chopper on Tuesday crashed in a spot where the river is 50 feet deep, officials said.

Dan Sweeney, a manager at the NYC Water Club, said he saw the splashdown.

“It went down pretty fast, you could see the splash, you could see the top of it and it just disappeared,” he said. “It looked like it was trying to land at the heliport and missed the landing.”

Two female passengers were in critical condition at a nearby hospital, one man was in serious condition at another hospital and one man was treated at the scene. The condition of the final passenger pulled from the water was not immediately known.

The aircraft is being identified as a Bell 206 Ranger and was not owned by a tour company.

The U.S. Coast Guard said pulling the submerged helicopter out of the water will require a crane on a barge with a sling attached. The aircraft will be pulled up and then the barge will be floated to a location where the National Transportation Safety Board can take over the investigation.

Two helicopters crashed in the East River in 2005, just three days apart. A sightseeing chopper with seven people aboard crashed on June 14, and a corporate chopper with eight aboard crashed June 17. There were no fatalities in either case.

Two years later in July 2007, a sightseeing chopper with eight people aboard crashed in the Hudson River, and again, there were no fatalities.

UPDATE 4:06PM EST: A helicopter with as many as five people aboard crashed in the East River on Tuesday and a rescue operation was underway, police said.

The privately-owned chopper was apparently trying to land at the helipad on E. 34th St. when it went down around 3 p.m. and quickly submerged.

Within minutes a police dive team was in the choppy water and quickly found four survivors and dragged them to shore.

Two of them were placed on stretchers and taken to Bellevue in serious condition, police said.

Divers and at least seven NYPD boats continued to scour the water for anybody else who might have been aboard the Bell 206 chopper.

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UPDATE 3:41PM EST:A total of four people have been removed from the chopper – which is reportedly submerged under water. One female passenger is still missing. Divers are continuing to search the water.

UPDATE 3:32PM EST: Five people are confirmed on board the chopper. Three people have been extricated by NYPD Divers, and are reportedly unconscious.

3:25PM EST:

A chopper is confirmed to have crashed into the water on the FDR Drive and 34th Street. Multiple people are trapped inside. Numerous emergency agencies are responding.

FURTHER DETAILS TO FOLLOW