The escalator in the northern end of the station was moving in upward direction when suddenly it started moving downwards at around 8.30 PM, Metro Railway Senior PRO Indrani Banerjee said.
Out of the nine injured persons, six were administered first aid at the station while three others were sent to a hospital, she said.
Metro Railway General Manager A K Kapoor ordered a high-level probe into the incident and asked for a report within two days, Banerjee said.