Yesterday, Inspector Jacqueline Whittaker said when police arrived the situation was difficult and unsafe.
The team investigating the incident were yet to speak to all staff who attended, she said.
"The facts haven't been established yet. There is a lot of speculation," said Ms Whittaker.
"There are a large number of people being interviewed, including police staff and party-goers. It will be investigated fully."
She said all officers who attended the party were still working.
The complaint is also being investigated by the Independent Police Conduct Authority.
Ella told RadioLive yesterday she decided to speak to the media because the officer hurt her and "I don't want him to get away with this".
"If this is happening on a regular basis it can't just go unnoticed because he's a policeman. People need to realise that this is happening a lot more than they think. I knew many people at the party who got hurt that night."
Ms Whittaker hoped the investigation, which would include reviewing photos and footage, would be wrapped up in two to three weeks.
"It's an absolute priority, we've got extra staff working on the investigation. This is an extremely unfortunate situation for everyone."