The New York-bound Amtrak train that derailed in Philadelphia, killing seven and injuring more than 200, was traveling faster than 100 miles per hour, according to the National Transportation Safety Board.

The agency said in a Twitter post that the further calibrations are being conducted after the preliminary data showed how fast the train was moving. The limit on the curve where the accident happened Tuesday night was 50 miles (80 kilometers) per hour, said an official briefed on the data, who asked not to be identified because the information isn’t public.

“We’ve suffered a tragedy here in our city,” Mayor Michael Nutter said Wednesday at a news briefing. “I don’t believe that anyone sitting here, standing here today has any memory of a derailment of this kind in 50 years.”

Nutter said he’d “never seen anything so devastating.”

“It’s an absolute disastrous mess,” he added.

According to the mayor’s account, about 150 people “self-evacuated” from the train, which Amtrak officials said carried about 240 people, including five crew members.

The derailment appeared to be the worst rail accident in the busy Northeast corridor in many years. No cause was immediately known. Federal investigators were sent to the scene, in a Philadelphia neighborhood that is northeast of the 30th Street Station.

Service in the Washington-New York corridor was shut down. It was not clear when it would restart.

Seven cars derailed, and some overturned.

They were in “horrible shape,” Nutter said at the news conference.

Some of the injured were freed after first responders cut them out of the wreckage, authorities said. About 200 police officers and 120 fire department personnel were at the scene, Nutter said.

Witnesses said the derailment apparently occurred on a curved section of track.

An employee of the Associated Press who was on the train — Amtrak No. 188 — reported that it appeared to be slowing down and then shook.

People’s belongings hurtled over his head, he said.

It was not clear how many of those who boarded the train in Washington remained on board as it left the Philadelphia terminal. A Philadelphia news site reported that Sen. Thomas Carper, D-Del., had left the train in Wilmington.

There were multiple reports on Twitter feeds that there was smoke in at least one of the cars. According to one of the messages, passengers who were able to move were trying to get the door open so they could climb down from the car, which was apparently on its side. Another tweet came from someone who reported being in a car tilted at a 45-degree angle.

Video footage from the scene showed cars under the illumination of floodlights as rescue workers’ flashlights swept across the silver sides of several of them.

The Philadelphia Police Department asked residents to stay away from the scene so first responders could operate more efficiently.

Authorities said the train was scheduled to leave Washington’s Union Station at 7:10 p.m. and arrive in Philadelphia about two hours later.

The Federal Railroad Administration was sending a team of investigators to the site.