Delhi Metro's Violet Line services were severely affected during the morning rush hours on Friday due to a major signalling glitch.
Services slowed down along the entire corridor stretching between Faridabad and Kashmere Gate after trains lost touch with the control centre, a metro official said.
As the centralised control mechanism snapped, trains had to be manually controlled, from each station, on this section between 8 am and 9 am, leading to long delays.
"The issue was resolved at 9 am and trains are now being regulated as per normal schedule on Line-6," a Delhi Metro Rail Corporation (DMRC) official said.
Earlier this year, following power failures and subsequent loss of contact of trains with the control centre, services were crippled on the Blue Line for two successive days.
Trains had lost contact with the Operational Control Centre, considered the nerve-centre of the metro network, due to sudden power failures, following which the alternative mechanism of station-level handling was activated.