A witness said that at the beginning of the night he saw a few girls in the EQ Tower lobby and a group of young men "running and yelling" outside around 4am or 5am.
Another witness told Nine News she heard "horrendous screams".
"I heard these male and female voices screaming," she said. "The girl's scream was incredibly loud, it was screeching. Normally I would call the police but they went off down the road."
Commander Tim Hansen said a number of young people left the party immediately afterwards.
Asked whether the culprit or culprits were among the 12 people being interviewed, Comm Hansen said: "I don't think so."
"(It was a) fairly chaotic scene, there was obviously a number of people out the front," he told reporters.
"It would be fair to say they were upset, obviously, and quite emotive. However, the police members were never threatened or challenged and took control of the scene pretty quickly."
The young woman from Pakenham died at the scene shortly after 5am following a dispute between a group which had hired the apartment and another arriving later.
It's unclear what brought the second group to the apartment but Comm Hansen said there was no sign of forced entry.
Tributes pour in
Support was being offered to the African-Australian community, of which the victim and partygoers were members, he added.
Friends and family have also paid tribute to the woman, with one writing on Facebook: "Never thought Friday would be my last time on earth seeing you.
"You were such a beautiful soul and didn’t deserve any of this ... forever remembering the memories we had. Fly high. RIP my beautiful princess I love you."
The young woman's family is believed to be from South Sudan.
Fairfax reports the Federation of South Sudanese Associations in Victoria chairman, Kenyatta Dei Wal, visited the family of the victim on Saturday.
"Her very young life has been cut short and the community is deeply distraught and in shock," he said. "The parents are deeply devastated."
Achol Marial, a youth affairs officer for South Sudanese Community Association in Victoria, urged people not to take revenge for the young woman's death.
"My community, please do not take matters into your own hands," she wrote on Facebook, according to Fairfax.
"Allow law enforcements to take their course, there is no need to revenge or avenge kill. We need to practise this skill here in Australia if we are to take the same mindset back home. We should also preach the same perspective to our families back home in South Sudan.
"We should stop supporting avenge deaths; I know it's painful, I know it's hard but it doesn't make the situation easier for the family members who are involved. South Sudan is falling apart purely because of this and we need to do better!"
'Tragedy that has been building'
About a quarter of the EQ Tower apartments are short-term stays, according to Melbourne Real Estate which manages rentals in the A'Beckett St address.
One of its residents, Sean, said this was a growing problem in the tower.
"This is a tragedy that sadly has been building and building over the last few months," he said.
"What we're seeing increasingly is these parties of youths getting out of control. They seem to come and go at short notice. Many of them are obviously intoxicated or on other substances. As residents, we feel intimidated that we're unable to ask them to keep the noise down."