A section of a packed subway train flew off the tracks and careened into a wall in Harlem Tuesday — forcing hundreds to crawl out onto the tracks to safety and crippling service citywide.
Some 34 straphangers were injured when two cars of the Brooklyn-bound A train veered off the tracks outside the 125th St. station about 9:45 a.m., authorities said.
MTA officials said the train’s emergency brake was activated before the derailment but investigators were still working to determine what caused it.
“The train was peeled open like a can opener,” said Paul Navarro, track division chairman for the Transport Workers Union, after visiting the accident site.
Straphangers described a harrowing scene as the train came to a screeching halt before smoke poured into the darkened cars.
After being trapped for several minutes, panicked riders on the A train and a trailing D train broke windows on their subway cars and climbed out onto the tracks.
“I didn’t even have a ladder,” said Emma Virani, 27, of Brooklyn, who was on the D train. “I had to jump out.”
Kelly Kopp, 48, said he heard what sounded like a “huge explosion” before his A train came to an abrupt stop.
“It was enough to scare the heck out of us and for me to think I could die in this train,” said Kopp, a photographer who was on his way downtown.
“As soon as the train stopped, people started screaming. And that was really terrifying because I thought some fire was going to start shooting through the train. And then people were throwing up, too, from the smoke.”
Joe Lhota said at a hastily convened press conference that it was unclear why the emergency break was deployed.
“This does not look like a failure on the part of the equipment,” Lhota said.
“The brakes went into emergency and we need to determine why,” added Lhota on just his fifth day on the job.
Some 17 riders were rushed to local hospitals with non-life-threatening injuries. The other half were being evaluated at the scene, FDNY Commissioner Dan Nigro said.
Following the derailment, three other trains were stuck in tunnels between 110th St. and 135th St., trapping a total of roughly 800 riders.
About 500 of them scrambled onto the pitch-black tracks, prompting a massive response from first-responders.
Some 200 firefighters and 100 police officers rushed underground to shepherd them to safety. It took more than an hour for all of the riders to make it above ground, officials said.
“The people who ended up on the tracks self-evacuated,” Nigro said. “It’s a very dangerous thing to be on the tracks.”
The incident crippled the subway system during the morning rush-hour — knocking out service on the B and C lines and large swaths of the A and D lines.
Lhota and Ronnie Hakim, the MTA’s acting executive director, said there was no telling when subway service would be fully restored.
Lhota said workers still had to remove the derailed train to determine the extent of the damage to the tracks.
“Our goal is to get back and running and quickly as possible,” Lhota said.
Lhota added that the smoke condition was caused by debris on the tracks that went up in flames.
After surveying the accident site, Navarro said the derailment caused “extensive damage” to the tracks and other key equipment.
“It took down the signal. It took down pieces of wall,” Navarro said.
He added that a piece of the train car door struck the electrified third rail, which was itself dislodged.
Navarro said that likely generated smoke and sparks.
“The train went into the wall and it peeled the door back,” he added. “Pieces of the door fell off the train and breached the third rail.”
The derailed train cars were found leaning against the tunnel wall, sources said.
The out-of-control train left a trail of bent and twisted track parts, according to photos obtained by the Daily News.
A photo taken of the side of the A train — and obtained by WABC-TV — shows a heavily damaged car with what appears to be a gaping hole at one end.
A total of three trains were stuck between stations when power was cut and the riders needed to be evacuated, sources said.
Rider Kirk James, 42, said the derailed A train came to a jarring halt while it was pulling into the 125th St. station.
“People kind of toppled,” said James, an NYU professor.
Several minutes passed with no sign of help. Then the smell of smoke wafted into the car, James said.
“People started panicking,” he added. “Again there’s no announcement. We’re smelling smoke now. We can’t open the doors. No one knows what to do.”
James eventually made it out onto the platform by walking to the front of the train. Along the way, he saw dazed riders out on the tracks being aided by firefighters.
“People are crying, people are grateful to be alive but no one knows what just happened,” James said. “There was no one there to say anything.”
The MTA reported a loss of power at 125th St. after 9:30 a.m., holding up A, C, B, and D trains.
“@NYCTSubway lights and a/c went out on train and train came to a full stop. What’s going on? Downtown A train about to pull into 125th,” Jenny Loeffler wrote on Twitter.
The MTA’s subway alert feed on Twitter said crews were working on bringing power back but had no estimate for how long it’ll be out.
Still, some took the derailment in stride — and joked about it.
“@mta you are the BEST!!!!” wrote Carrie Courogen. “It was so much fun living out my horror film fantasies. Especially the part when the train was like sideways!!!”
The derailment was the latest in a series of subway mishaps that caused chaos underground and prompted calls for a full overhaul of the aging system.
It forced the MTA to stop all A trains between Jay St. and the Inwood-207th St. stop. B train service between Brighton Beach and 145th St. was suspended, according to the MTA’s website.
By 3 p.m., there was still no service on the B and C lines.
The A line was out between 59th St. in Midtown and 207th St. in Inwood, and there was no D train service between 59th St. and 161st St. Yankee Stadium.
The M line was out between Queens and Brooklyn.
“It’s horrible — a total horror,” said Phyllis Akerley of Howard Beach, while riding an A train from Howard Beach to Jay St.
“It should’ve been 40 minutes and instead it’s been an hour and 20 minutes, and we’re still not there yet.”