A private helicopter made a crash landing on the roof of a midtown office tower this afternoon. The pilot is believed to have been killed in the crash, with no other injuries reported at this time. Below, read our breaking news updates in reverse chronological order:

Update 4 p.m.: Mayor de Blasio confirmed that Monday afternoon's helicopter crash on the roof of a Midtown Manhattan building was not an act of terror. "There is no danger of any kind to New Yorkers at this point," he stressed during a press conference this afternoon. "One person died in this helicopter crash, that person is presumed to be the pilot...there does not appear to be any passenger in the helicopter." He added they do not know the cause of the crash yet, and there were no other injuries to anyone in the building or on the ground.

FDNY Commissioner Daniel Nigro said that the fire caused by the crash has been extinguished, but "there is some amount of fuel leak" which has now been mitigated. The building, located at 787 7th Avenue, has been deemed safe, though no one has been allowed back in yet. Some debris fell onto a set back on the building, but not the street. It was also mentioned that firefighters had to pump water over 700 feet to reach the roof.

Police Commissioner James O'Neill said the plane took off at 1:32 p.m. from the 34th Street heliport by the East River, and crashed 11 minutes later at the building. The helicopter was privately-owned, they believe its purpose was for "executive travel" and it may have been headed back to its "home airport" in Linden, NJ. He added that they do not believe the pilot was the owner, and it is unclear whether there were any distress calls before the crash.

Update 3:20 p.m.: Police have now closed everything from 42nd to 57th streets between 8th Avenue to 6th Avenue to all pedestrian and vehicular traffic as they continue investigating the incident—including reports of "fuel leaking from the helicopter."

Vinny Tirmal was working in the building at the time of the incident when he was suddenly told to evacuate: "We just heard the ground shake, thought it was an earthquake, and then we went back to business," he said. "And then we got notified to evacuate."

"I was in my office on a phone call with a client, and I felt the building shake," said Susan Stolzer, who works on the 26th floor of the building. She said the building was evacuated in an orderly fashion, and everyone dispersed when they got downstairs. "We haven’t heard anything yet about when we can go back. We don’t know whether or not the building will be open tomorrow."

NBC Aviation Safety Analyst Greg Feith is reporting that the helicopter was privately owned: "Pilot contact ATC and said he needed to land immediately - additional information from ATC about the possible reason for the necessity to land will be critical. The reasons are many - weather, spatial disorientation, mechanical malfunction or failure, etc."

The FAA adds that at the time of the crash, Newark Airport and LaGuardia Airport were both at a ground-stop due to poor visibility and thunderstorms. A video has now emerged of the helicopter allegedly flying erratically prior to the crash:

Helicopter rooftop landing pads were mostly banned after five people were killed in a helicopter crash in May 1977 on the roof of the Pan Am Building in Midtown. Last week, Uber announced it would be launching a helicopter service from JFK to Manhattan next month.

[Update 2:55 p.m.]: The FDNY has confirmed that one person was killed in the helicopter crash; both the Times and ABC are reporting the victim was the pilot of the helicopter.

Katie Pizzani, who works nearby on the corner of 52nd and Broadway, heard the commotion outside when the crash happened: "We're around Times Square and we hear that stuff all the time," she told Gothamist. "Then it got much louder and there was a lot of commotion. We all got the Citizen alert and we started watching the live feed, and it got a little bit scarier. There's tons of ambulances, cops, firetrucks—there's no traffic at all on Broadway right now. They completely shut down all the streets."

Gov. Cuomo is at the scene now, while Mayor de Blasio is en route there. Cuomo told reporters that there was no indication this was terrorism-related: "If you’re a New Yorker, you have a level of P.T.S.D., right, from 9/11," Cuomo said. "I remember that morning all too well."

When asked about limiting helicopter use in the city, Cuomo told NY1 that helicopters are an "important part of transportation system in NY obviously," adding, "I don't think its about helicopters or small planes, that's part of NY, accidents will happen."

A senior FAA official told ABC News this is believed to be an accident and the helicopter lost contact with the LGA tower.

The MTA adds that several bus routes that travel through Midtown Manhattan are "detoured and delayed" while the NYPD and FDNY continue the investigation into the crash. Check mta.info for updates about service.

[Initial Report Below]: First responders are investigating reports that a helicopter has crashed into a building in Midtown.

An NYPD spokesperson said they are investigating reports of a helicopter crashing into a building at 787 7th Avenue at 51st Street, around 1:40 p.m. on Monday. Firefighters and police are on the scene now. The NYPD is now describing the crash as a "hard landing" on the roof. The landing caused a two alarm fire at the 54-story building, which officials say has been extinguished.

The building was being evacuated as of 2 p.m.:

The area around the crash has been closed off by the NYPD as well:

Governor Andrew Cuomo was asked about the incident at a press conference:

We'll update the post as we learn more information.

With additional reporting by Danny Lewis and Adwait Patil