CHENNAI: About 25 commuters were stranded in a metro train in the underground tunnel between Chennai Central and the Madras High Court stations in the early hours of Tuesday. The train stopped midway as the power supply to the controlling units was cut off. The commuters were made to walk through the tunnel to the High Court metro station, a video of which went viral, and were safely received by the station manager.The incident occurred in the blue corridor of CMRL, connecting Chennai airport with Wimco Nagar, between 5.15 am and 5.45 am. After leaving the Chennai Central underground station, the train suddenly stopped midway before reaching the High Court station. The train operator alerted the operation control room and safely evacuated the passengers as per procedure. The tunnel lights were switched on, and the passengers were counted before being taken to the station. They were counted again to ensure that all passengers were safely out of the tunnel.CMRL officials said that the controlling unit of the metro trains is operated through batteries. “There are two batteries which draw power from the source. If one fails, the other will work as a backup. But both the batteries failed to power up the control units, so the train stopped. It is the first time we encountered such an issue,” said an official.The defective train was pulled back to Chennai Central and parked on a siding track, as the train could not be powered up. “It will be shifted to Koyambedu yard tonight for further investigation,” added the official. CMRL said that normal operations resumed at 6.20 am.