"An escalator near gate number six (that opens to F Block) which was moving upward from subway to ground level started slipping in reverse direction.
"There were around 25 passengers on the escalator at that time, of which four persons got injured.
The injured were taken RML Hospital by CISF," the official said.
The injured, including one woman, received minor injuries in neck and feet, a CISF official said.
They were discharged after being administered medical aid, a metro official said.
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"The reason behind the incident is being investigated," a metro spokesperson said.
An FIR under sections 287 (negligent conduct with respect to machinery) and 337 (causing hurt by act endangering life or personal safety of others) of IPC has been registered into the case and the injured would be medically examined, a senior police officer said.
"Necessary action to jointly check and investigate has been taken to look into this failure," DMRC said.