A driverless metro train on a trial run in New Delhi crashed through the wall of the Kalindi Kunj depot in South Delhi on Tuesday, ANI reported.

The mishap comes just days before Prime Minister Narendra Modi is scheduled to inaugurate the Delhi Metro’s Kalkaji Mandir-Botanical Garden line on Christmas Day. Unmanned trains will ply on the route in about two to three years, NDTV reported.

The Delhi Metro Rail Corporation said the accident occurred because the maintenance team did not check the train’s brakes before the trial run. The metro authority has ordered a high-level inquiry into the incident, saying a committee of three of its officers will look into it.

The corporation said the train was being operated manually when it was taken to the Kalindi Kunj depot to be washed. When the operator moved the train up a ramp, it slid backwards because the brakes were not working.

Kalkaji Mandir is a station on the Violet Line in South Delhi, and Botanical Garden is located on the metro’s Blue Line in Noida. The new line, known as the Magenta Line, will reduce the travel time between South Delhi and Noida.

The first phase of the 12.64-km-long Magenta Line will have nine stations – Botanical Garden, Okhla Bird Sanctuary, Kalindi Kunj, Jasola Vihar Shaheen Bagh, Ohla Vihar, Jamia Milia Islamia, Sukhdev Vihar, Okhla NSIC and Kalkaji Mandir.