Victoria Police are currently attending the scene of the incident between Elizabeth Street and Swanston Street.
The driver of the car has been arrested by police.
According to Ambulance Victoria, at least 12 people were being treated by ambulance officers at the scene.
Police says, the 32-year-old Heidelberg West man alleged to be the driver has been released from hospital and is currently in police custody.
He is an Australian citizen of Afghan descent.
Crime Department detectives will interview him once he has been medically cleared.
The off-duty police member who arrested the driver remains in hospital has undergone surgery and is stable.
The 24-year old man arrested on Flinders Street, who was not involved or connected with the initial incident, has been interviewed and released.
He is expected to be charged on summons with possess cannabis and possess controlled weapon.
These offences are not linked to the initial incident.
