Hazy smoke filled a Brooklyn-bound G train during the morning commute, sending panic-stricken passengers scrambling for an exit and covering their mouths as crews worked to clear the scene.

Riders say the frightening ordeal is something they won’t soon forget.

“As somebody who takes the G train every day for work, that is out of this world,” said commuter Kalini. “I can’t imagine being on the train and there’s smoke like that. That’s crazy.”

MTA spokesperson David Steckel says a mechanical issue was behind the smoke. Steckel says a "review reveals the [G] train hit an object on the tracks that has yet to be recovered, causing a third rail contact shoe to spark." Exposed wires generated smoke "that penetrated the interior of the train."

Passengers were safely evacuated at 21st Street, and service was temporarily suspended between Bedford-Nostrand Avenue and Court Square. The disruption left many riders frustrated as they faced significant delays.

“It’s a little frustrating because I’m trying to go get my kids, trying to pick them up,” said Yaakov, who had been waiting for about 45 minutes. “I’m already running late.”

Others described confusion after being directed out of stations and back through turnstiles, only to be told to seek alternate routes above ground.

“It’s impossible to use the G train right now,” said commuter Yoki. “The information that I received on MTA is that the train is running, and now that I’m at the station, I’m told it’s not running either direction.”

To ease the disruption, the MTA offered alternate travel options, including the B43 and B48 buses to Greenpoint, and the B62 between Greenpoint Avenue and Court Square. Still, reactions among commuters were mixed.

“A lot of people are pissed off. They’re being late now. You can even lose your job,” said Nelson Espinosa. “But for me, I’m just going to see my kids. I’ve got all day to go. I’ve got plenty of time.”

Others urged patience amid the chaos.

“You just gotta be patient,” said Taj.

Steckel says an internal review remains ongoing