The incident occurred at 3:40 pm and the impact of the crash had left the eyewitnesses in shock.
The train was supposed to go forward but it ran backwards breaking through the boundary wall of Kalindi Kunj depot. The front portion of the metro train and a stretch of the depot's boundary wall was damaged.
The mishap comes less than a week before PM Narendra Modi inaugurates the new Magenta metro line from Botanical Garden in Noida to Kalkaji Mandir in Delhi on December 25.
"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. No person was injured in the incident," the Delhi Metro said in a statement.
"MD, DMRC has ordered a high level enquiry into this incident by a committee of three officers of the rank of Executive Directors.
"Prima facie it appears, to be a case of human error and negligence and appropriate action will be taken after the inquiry," it said.
The DMRC said 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," it added.
The Kalkaji Mandir-Botanical Garden line of the Delhi Metro will reduce travel time between Noida and south Delhi.
The 12.64-km section, part of metro's upcoming Botanical Garden-Janakpuri West (Magenta) Line, was granted safety approval by the Commissioner for Metro Rail Safety (CMRS) last month.
Metro's new generation trains, which can run without drivers, will run on this section where an advanced Communication Based Train Control (CBTC) signalling technology that will facilitate movement of trains with a frequency of 90 to 100 seconds will also be pressed into service.
However, for an initial period of two-three years the trains will have drivers.
Currently, for travelling to south Delhi areas, commuters from Noida have to change trains, from Blue Line to Violet Line, at Mandi House Metro Station.
After the new section of the Delhi Metro is opened, commuters will be able to travel directly to Kalkaji Mandir Metro Station, which is on the Violet Line, cutting travel time by about 45 minutes.
Once the entire corridor from Botanical Garden till Janakpuri West (38.23 km) is opened, commuters from Noida will be able to go to Gurgaon by changing trains at Hauz Khas.
The Botanical Garden has been developed as the metro's first-ever inter-change station outside the boundaries of Delhi.