Straphangers aboard the A train on Tuesday, June 27, 2017. View Full Caption Skip Suva

MANHATTAN — More than 30 people were hurt and dozens evacuated when the brakes on a southbound A train were abruptly triggered, sending two cars off the rails and into a wall near the West 125th Street station and tearing a door off one car, riders and officials said.

The train was approaching the 125th Street station about 9:48 a.m. when the emergency brake activated, throwing terrified riders from their seats as lights started flickering and sparks flew outside their windows before the whole train came to an abrupt stop, witnesses said.

"It was a bit of a rough ride. Then it felt like the train was jumping. I was like, 'This is serious.' All of a sudden, I saw what I thought was a flash or explosion. I wasn't sure. It all happened so quick. A car went off, then the train stopped. People were screaming. It was chaos," said Kelly Kopp, a 48-year-old photographer who was on the second to last car.

"People were throwing up, people were screaming. I thought I might be caught in some fire. I was terrified," Kopp added.

Straphangers were evacuated through the dark as the cars filled with smoke from garbage that caught fire from sparks caused by the crash, officials said.

Newly reappointed MTA Chairman Joseph Lhota said he wouldn't know what caused the emergency brake to trigger unit the investigation was completed.

"The emergency brake automatically went on. The train bucked forward. It bucked backward," Lhota said.

The head of the Transit Workers Union Local 100 said that the derailment caused extensive damage.

"It’s a serious derailment, with quite of bit of damage to signals and some structural damage to the walls," the union's vice president for the Maintenance of Way Division, Tony Utano, said. "Our members are working as fast and safely as possible to bring the system back to normal."

MTA officials said it would be unclear how much damage was caused until they could remove the train.

Subway service through the area would be suspended until they could properly investigate the scene, Lhota said.

Meanwhile, riders who were back above ground recounted their terrifying commute.

Commuter Skip Suva, 28, was riding on a southbound A train approaching 125th Street just before 10 a.m. when he said "the train started shaking insanely violently, the lights started flickering. I was leaning against the left door, on the left side of the train, and the right door was ripped open."

"It was really dark, tons of smoke and dust, and white chunky things," he told Gothamist. "There was a lot of distortion on the floor. The metal was pushed in, and either the door was jammed... or it was totally pulled off, like, opened like a book."

Danny Jimenez, 30, of Washington Heights, was in the fourth car and heading to his library job when the derailed, he said.

"It just hit something. It shook. Then we saw sparks out the window. They were big sparks, about 5 feet high. They were at the top of the window. Then there was a strong gas smell," Jimenez said.

Carrie Courogen, of Washington Heights, said "we were going fast and all of a sudden I felt this big bump, like it went up in the air and rocked side to side in the air, off the tracks. I flew up onto my seat and onto the ground. It came to a screeching halt. We saw sparks. It smelled so bad, like burnt rubber."

Courougen said riders were desperate to escape and several people tried to open windows or doors to get out during a harrowing period with no information from the conductor as smoke built up in the car.

"We were just sitting there and no one tried to tell us over the intercom. We had no idea what was going on. Finally after 10 minutes the conductor gets on and she's like, 'We have a derailment, we're coming through the cars,'" Courougen said.

Some riders pried open the doors and escaped into the tunnel, said Lhota, who added that riders should never do that.

"We were sitting there for so long with no information, and as time went by there was more smoke in the car," Courougen said. "The not knowing was terrifying. As we were leaving there was an older gentleman who had a cane and he was waiting for medical personnel, and said, 'I think I need to go to the hospital.'"

As of 12:30 p.m., 34 people suffered injuries that weren't considered life-threatening, an FDNY spokesman said. Seventeen of those people were treated at New York-Presbyterian and Harlem hospitals while the rest were being evaluated on scene, officials said.

In total, about 1,300 people had to be evacuated from seven trains that included the derailed A train and three others that were stuck in tunnels nearby, sources said.

About 500 of those people had to be brought up to safety by walking over the tracks, but in order to do that, officials had to turn off the power to the third rail, which stopped trains in nearby tunnels, sources said.

The other 800 were able to evacuate through trains that had cars in stations, sources said.

"It was a very difficult operation, operating below ground with that many people," said FDNY Commissioner Daniel Nigro.

"The operation took place between 110th Street to the south and 135th Street to the north. The department deployed folks north and south of this station. They went down onto the tracks in three locations. That's where those trains were stopped," Nigro added.

The MTA initially blamed a power outage for the derailment, but didn't provide further details. They refused to confirm whether a train had derailed for nearly an hour after the crash, saying only that a "subway incident" had occurred. They finally confirmed a derailment shortly before 11 a.m.

Service along the A, B, C, D, E, F and M trains were disrupted throughout Brooklyn, The Bronx, Manhattan and Queens, according to the MTA website. Commuters should check the MTA's site for the latest updates on each line.

"We're doing the best we can to get service up and running as quickly as possible," Lhota said.

Riders uploaded photos to social media showing emergency workers on the subway tracks.

Meanwhile on the A train this morning. pic.twitter.com/AdyM1ohSKz — N.RI.K (@nrik_nyc) June 27, 2017

Train derailment near 125 A train. Huge bang, sparks and smoke. We were stuck underground for a while but it seems nobody was hurt. pic.twitter.com/aXdUFJhlNS — Gabriela C. Martinez (@gcmarts) June 27, 2017