A Delhi metro train crashed into a wall on Tuesday at Kalindi Kunj depot when it rolled back on a ramp while being taken for washing, six days before its commissioning with the scheduled launch of the magenta line by the prime minister.
There were no casualties, according to the Delhi Metro Rail Corporation which blamed the incident on "human error and negligence" during maintenance and asserted it will have no bearing on the December 25 launch.
A DMRC official said that the empty train, part of metro's new generation 'driverless' fleet, broke through a portion of the boundary wall at the depot around 3.40 pm as it rolled back.
"A trial train was moved from the workshop without testing the brake system as a result of which, while the train was moving up the ramp for washing, it rolled back and hit the adjacent boundary wall," the DMRC said in a statement.
The end of the train which hit the wall suffered damage and a portion of the wall collapsed, suggesting that the collision was quite intense.
A high-level inquiry by a committee of three officers of the rank of executive directors has been ordered, the DMRC said.
"Prima facie, it appears to be a case of human error and negligence and appropriate action will be taken after the inquiry," the DMRC statement said.
The Managing Director of DMRC, Mangu Singh, said that "main line operations on this line are absolutely safe, with a high level of automation and has been thoroughly checked and cleared by the commissioner of metro rail safety for passenger operations ."
"Today's incident was a manual error during maintenance and has nothing to do with the trials or passenger safety during future operations," he said.
The Delhi government, meanwhile, also sought a report from the DMRC on the incident with Transport Minister Kailash Gahlot tweeting: "Shocking lapse! There can be no compromise on passenger safety."
The DMRC and the Delhi government are engaged in a running feud over the recent rise in commuting fares. The Arvind Kejriwal government continues to insist that the fare hike should be rolled back.
The train was to be pressed into service on the 12.38-km- long Botanical Garden-Kalkaji Mandir section, which is part of the magenta line coming up as part of metro's Phase III construction.
Only on Monday, the DMRC had announced that the section will be inaugurated by Prime Minister Narendra Modi on December 25.
The inauguration was very much on track, a metro official said, stressing the accident will "not have any bearing" on the services on the new corridor.
As per DMRC's laid down norms, when a train enters a workshop (depot), the brakes of the train are decommissioned so that the train and its systems including the brakes can be freely checked.
Once the train is again re-commissioned, the brakes are tested by the maintenance staff in the depot before the train leaves the shed. The train movement inside the workshop area is done manually and not by the signalling system.
"Prima facie, it appears, this was not done and subsequently, the person who took charge of the train from the maintenance staff also did not check the brake and proceeded with the train up to the washing plant built on a ramp. While stopping at the ramp, since the brakes were not available, the train rolled back causing this incident," the DMRC said.
Otherwise, when a train is on service, its brakes are largely guided by the automatic signalling system and controlled from the Operations Control Centre, one of which is housed inside the metro headquarters itself.
Earlier, in November 2016, two trains, on trial, had grazed each other at the same depot.