The incident, which affected services on Yellow Line, happened around 10.20 am when the Samaypur Badli-bound train was entering Rajiv Chowk. It was evacuated at the station itself and there was no injury to any passenger.
"A minor smoke was reported from the air-conditioning vent of the last coach of a metro train at Rajiv Chowk platform heading towards Badli. As a precautionary measure, the train was evacuated at the station itself and passengers were accommodated in the next train," a Delhi Metro official said.
According to eye-witnesses, sparks first appeared when the train entered the Central Secretariat station and it reappeared after it went Patel Chowk station towards Rajiv Chowk.
Many passengers took to Twitter immediately after the incident, somewhat shaken by the explosion-like noise that accompanied the spark and smoke.
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"Witnessed two explosions at Rajiv Chowk 15 mins back. What's happening? And again when it reached Rajiv Chowk," read one post, while another tweet said: "Something's not right at #RajivChowk. 2 explosions in electric box back to back."
Last December, thick plumes of smoke had engulfed a metro coach due to sparks in its air conditioning system, forcing the evacuation of a train full of panic-struck passengers at Patel Chowk station.
The 48-km-long Yellow Line (Line 2) stretches between Gurgaon's Huda City Centre and north Delhi's Samaypur Badli.