A two-decade-old Metro train spewed smoke from its undercarriage and stalled while pulling out of Mahatma Gandhi Road station on Monday evening, disrupting the transport lifeline’s peak-hour schedule for more than an hour.

The packed rake screeched and stopped while going towards Girish Park at 6.28pm after the driver noticed wisps of smoke coming out from under a coach. Four coaches of the train were then in the tunnel and the rest along the platform at the station.

Commuters in the coaches that had entered the tunnel remained stuck inside for at least 15 minutes before Railway Protection Force (RPF) constables joined Metro personnel in manually opening some of the doors.

The rake is part of an ageing fleet that remains in operation because Metro Railway doesn’t have a choice. According to a senior official who declined to be named, disruptions in service because of snags could become more frequent in the absence of newer rakes.

“There was a lot of panic inside. Some commuters said they were suffocating and at least one woman appeared to have fainted for a few moments. She was brought out on a stretcher. She came to after we splashed water on her face,” an RPF officer said.

Manoj Jha, who had boarded the train at Esplanade and was going to Shyambazar, said he knew something was amiss when the lights went off and didn’t come back. “It became pitch dark inside. The doors of our coach did not open and we had to walk into another through the vestibule to get out. I could hardly breathe by then. It was a nightmare. Some kids were crying.”

A few trains operated between Maidan and Kavi Subhash and Dum Dum and Girish Park stations after 7pm. Around 7.15pm, when a train entered Maidan station, a voice said over the public address system that it would turn back and go towards New Garia.

Metro officials said normal services resumed at 7.34pm but the ripple effect lasted well beyond that.

Thousands of commuters, most of them returning home from work, were stranded at other stations for some time before opting for other modes of transport. “I waited 30 minutes at Chandni Chowk station before coming out and hopped onto an overcrowded bus,” said Sandip Kar, a resident of Tollygunge.

The rake that caused the disruption has been taken to the Noapara car shed for checks, Metro spokesperson Indrani Banerjee said.

Around six lakh people travel by the Metro every day, a figure that is increasing every year. The current strength of the fleet is 25 trains, of which 13 are air-conditioned. Two old rakes were discarded — “condemned” in technical parlance — earlier this year.

Smoke from the undercarriage of the stalled train fills MG Road station as commuters are evacuated on Monday evening. Sanjoy Chattopadhyaya