Police were called to an incident in Doncaster on Wednesday evening (28 October).
Investigators have been told a group of male youths were fighting in a hotel carpark in vicinity of Doncaster and Williamsons Road about 5.40pm.
A 15-year-old boy remains in hospital with a serious head injury.
Police are yet to determine the circumstances surrounding the incident and the investigation is ongoing.
Investigators are seeking car or mobile phone vision from the vicinity of the incident which can assist with their enquiries.
Anyone with information is urged to contact Crime Stoppers on 1800 333 000 or file a confidential report online at www.crimestoppersvic.com.au