According to officials, all the trains slowed down at around 11.50 AM as they were not achieving their target speed which averages around 36 km/hour.
"So the speed had to be reset from the central control room of our operations," an official said.
That resulted in a chain reaction of sorts as trains got stuck in tunnels, elevated tracks and in stations for minutes end.
Blue Line or Line 3/4, which stretches over more than 50 KM long, is one of the busiest sections in the entire network, which is also the most snag prone.