Police Assistant Commissioner Richard Chambers told Checkpoint the conflict this evening was after protesters had moved a concrete block and police had to put it back.
"Obviously we sent some staff into the field to help, but there were no issues."
He said the three police who were hit with a stinging substance are doing "really well".
"We took them to hospital this morning as a precautionary measure but they're fine now."
At this stage they have not made an arrest but are focusing on next steps, he said.
It's still not known what the substance was. Chambers would not detail what sort of protest leadership police are talking to, but police negotiators are involved in talking to a group.
He said the funding of the protest from people like the Red Stag boss is no surprise.
The legality of funding the protest is something police are looking at, he said.
Chambers said he is not aware of a specific sexual assault complaint, but "there has been chatter" and is appealing for anyone who might have been harmed to come forward.