The 18-year-old from Eltham, south London, was held after the crash in Sir Thomas Longley Road, Medway City Estate, Strood at  22:16 BST on Friday.
Four men with serious injuries, aged between 20 and 50, were taken to King's College Hospital, London.
Another five people were taken to Medway Maritime Hospital.
Four people were injured but did not require hospital treatment.
Police said none of the injuries was life-threatening.
Officers were already at the scene dealing with reports of a disturbance involving nuisance vehicles when the accident happened.
"We are conducting numerous enquiries into this incident and would like to speak to anyone with information who has not yet spoken to officers," said Sgt Scott Lynch.
"A lot of people were in the area at the time and we believe that some of them may have video or pictures of the collision.
"I would like to encourage anyone with footage to get in contact with us as it could be vital for our investigation."
A teenager has been arrested on suspicion of dangerous driving after 13 people were injured when a car ploughed into a crowd on an industrial estate.