A 16-year-old girl was taken to a hospital in a critical condition after being caught in the Parramata bus.
Around 21.45 hours on Sunday, the bus traveled east along Argil Street as it climbed onto the pedestrian crossing on a church street and hit three female pedestrians and a bus shelter.
Two of the women have suffered minor injuries and were taken to Westmead Hospital for treatment.
The 16-year-old girl was trapped underneath the bus while she was released at 23.15.
She was taken to Westmid Hospital in a critical condition.
The male bus driver was also taken to Westmead Hospital for treatment to be shocked. A blood sample will be obtained from the man in the hospital.
It is believed that during the crash the bus contained a small number of passengers who were not injured.
There is a crime scene at the crime scene, and officials from the accident investigation department have begun an investigation.
Anyone who has information about this incident is invited to link to the mistakes: 1800 333 000 or https://nsw.crimestoppers.com.au.