The law enforcers also seized the bus from Oxygen area, said Mohammad Mohsin, officer-in-charge of Kotwali Police Station.
Driver Biplab Debnath was arrested at 12am and the number of the seized bus is Chatto Metro-J-11-1120.
The female CU student boarded the New Market-bound bus plying on route no. 3 from Gate-1 of the university around 3 pm on Thursday.
All the passengers but the victim got down from the bus at Reazuddin Road around 4:30 pm and the bus started moving towards Station Road changing its original route.
As the girl asked the driver to stop the bus out of fear, the bus helper rushed to her and tried to strangle her with her scarf.
Desperate to save herself, the girl hit the helper with her mobile phone, rushed to the door and jumped off the moving bus.
A case was filed with Kotwali Police Station on Friday afternoon accusing the driver and helper.