A power outage in the air-conditioned Metro rake that had caught fire on December 27 caused it to stall on the elevated track outside Dum Dum on Wednesday afternoon, triggering a two-hour disruption in service till Girish Park station.

The snag occurred around 1pm, moments after the rake had left Dum Dum for New Garia. Metro engineers suspect a cable under the train carrying current from the third rail came in contact with another piece of equipment, triggering the outage.

The rake remained where it had stopped — around 700 metres from Dum Dum station and 330 metres before the tunnel going to Belgachhia starts — for around 15 minutes. The driver tried fixing the glitch, failing which he informed the control room, a Metro Railway official said.

Passengers alighted from the coaches using a ladder in the guard’s cabin at the rear.

Metro services were restricted for two hours to the stretch from New Garia till Girish Park, one of the stations where rakes can switch tracks. The first New Garia-bound train after power was restored left Dum Dum at 3.14pm, the official said.

The schedule had gone haywire by then. The increasing interval between trains led to overcrowding.

“The display board at Kalighat station at 2.15pm showed the arrival time of the next Dum Dum-bound train as 2.19pm. But the train came at 2.24pm. It was so packed that I could not board it. The next train arrived at 2.43pm. This was also overcrowded, but it was getting late and so I elbowed my way in,” said a Chetla resident going to Esplanade.

The doors of some rakes did not close and open at one go because of the crowd crush. This further affected punctuality, which has been a challenge for the transport lifeline for a long time.

While Kalighat was packed with commuters, Belgachhia and Sovabazar in the north wore a deserted look for two hours. Most of the token counters were shut. “I reached Sovabazar station around 2.20pm and the counters were shut. A voice over the public address system kept announcing that a problem at Dum Dum station had led to curtailment of the route,” a commuter going to BBD Bag said.

The impact of the partial Metro paralysis was visible on the roads outside the affected stations. Commuters looking for alternative modes of transport milled outside Belgachhia, Sovabazar and Shyambazar .

Metro Railway’s latest disruption coincided with the second day of the Madhyamik exam. “I was accompanying my son to his exam centre in Dum Dum. I am scared to think what might have happened had this happened in the morning,” said a woman who lives in Shyambazar.

Indrani Banerjee, the official spokesperson for Metro Railway, said normality returned at 3.14pm after the stalled rake was taken to the Noapara car shed. “Wheel-slide protectors had to be placed under the rake so that it did not roll down during the evacuation. That took time.”

The snag-prone AC rake had been grounded for a long time after the December 27 incident. It was reinducted into the fleet only recently.

Metro coaches should have CCTV cameras and a “talkback system” that enables the driver to communicate with passengers, the commissioner of railway safety (eastern circle) has recommended in his final report on that incident.