Subway riders were trapped in a smoke-filled 7 train Monday night.
The Metropolitan Transportation Authority says it happened just before 11 p.m. after the train left Grand Central Station.
Officials say the conductor heard a popping noise and then saw smoke in the tunnel.
Power was shut off in the tunnel and passengers sat on the train for 20 minutes until authorities helped them out.
The problem is still under investigation, but no injuries were reported.