"One of these males had a backpack on that had been taken from one of the victims," Mr Underwood said.
"A second blue, black and white Quicksilver backpack and an olive green hunting jacket remain outstanding and we will be speaking to Wintec in regards to asking their staff and students to keep an eye out for them."
A 17-year-old, two 15-year-olds and two 16-year olds are assisting police with enquiries.
Mr Underwood said police were concerned that the youths were in the central city at 2.30am.
"With Labour Weekend starting tonight and secondary school exams about to commence, young people will have a lot more time on their hands and it is imperative they have appropriate supervision least we see a repeat of this morning's gutless, unacceptable behaviour."