A helicopter pilot has died in a fiery crash after making a forced landing on the roof of a Manhattan skyscraper.
New York Mayor Bill De Blasio says there is no ongoing threat to the city.
He said authorities do not know the cause of the incident.
New York Governor Andrew Cuomo said it appeared that the chopper made a "forced landing" on top of the 51-storey building.
The FAA says it was an Augusta A109E helicopter which crashed into the roof of 787 Seventh Avenue.
The FBI is involved in investigations.
The mayor told CNN that the victim was a commercial pilot who was involved in ferrying executives around. He said that it is "very unusual" but "we see nothing criminal" and "no act of terror".
Authorities are checking whether the pilot had authority to fly in the restricted area.
Officials told a press conference that the helicopter was privately owned, that the pilot has been identified and a potential path of the helicopter travel has been identified.
The helicopter was flying in heavy rain in airspace that is supposed to be off-limits.
A flight restriction in effect since US President Donald Trump took office bans aircraft from flying below 914m within a 1.5km radius of Trump Tower, which is just a few blocks from the crash site.
It wasn't clear why the pilot flew into that part of Manhattan, but authorities called it an emergency landing.
Bob Murphy was working on the 47th floor of the 51-storey building when the helicopter crashed into it.
He told Newstalk ZB he initially feared he was hearing a small plane heading for the building.
"It occurs to me that I'm being silly standing by a window, if it's a low-flying struggling prop plane, and maybe it's best I stand back.
"The next thing I know, I hear this huge bang, and it literally shakes the whole building."
Murphy said by the time everyone reached the ground floor, pandemonium had set in with emergency services on the scene.
The pilot was killed in the crash after the helicopter burst into flames.
The pilot was the only person aboard the Agusta A109E helicopter when it crashed about 1.45pm local time.
The weather in the area is poor, with heavy rain and strong winds.
The damage is believed to have been restricted to the top of the building, identified as the Axa Equitable Centre on Seventh Avenue.
People inside the building had felt a large shake and a fire broke out.
The New York Police Department said the incident happened at 787 Seventh Ave.
"If you're a New Yorker, you have a level of PTSD, right, from 9/11,'' Cuomo said.
"I remember that morning all too well."
The Federal Aviation Administration said there was no indication the crash was terrorism-related.
Several nearby buildings have been evacuated.
Nathan Hutton was on the 29th floor of the building struck by the helicopter said: "We could feel it when it hit but no one knew what it was."
The fire alarms activated and security told the occupants to get out of the building via the stairs, Hutton said.
Evacuating the building took more than 30 minutes down crowded staircases.
Videos posted by onlookers showed emergency vehicles in the street, but no obvious damage to the skyscraper, which is about 229 metres tall.
Pedro Rodriguez, a pastry line cook at Le Bernardin, a well-known restaurant in the building, said workers got an announcement telling everyone to exit, and he later heard from people around him that there was a fire on the roof.
The evacuation wasn't chaotic, Rodriguez said, but he was rattled because he immediately thought of the September 11 attacks.
Alex Jacobs was working on the seventh floor when he heard bells and an announcement to evacuate. He and his colleagues - who hadn't heard or felt an impact - used stairs to a fire exit.
"It's really unfortunate. I Just hope everyone's OK," he said.
The crash scene is about eight blocks from Central Park.
New York's grim helicopter history
The NYPD says pedestrian and vehicular traffic is barred from 42nd to 57th Streets between 6th and 8th Avenues in Manhattan after the crash.
New York City has a history of both minor and major helicopter wrecks and crash landings.
Last month, a helicopter crash landed in the Hudson River near a busy Manhattan heliport. The pilot escaped mostly unscathed.
Five people died when a sightseeing helicopter crashed into the East River last year.
Three people died in another crash into the same river in 2011.
Nine people died in a collision between a sightseeing helicopter and a small plane in 2009, not far from the scene of today's crash.