The violent clashes on Manus Island that left an Iranian asylum-seeker dead happened after local G4S descended on protesting asylum-seekers, a preliminary police report has found.
A Papua New Guinean police spokesman has told Fairfax Media that 23-year-old Reza Barati was killed by multiple blows to the head, probably from a piece of timber.
The post-mortem, carried out on Monday, found that the blows caused a blood clot on the man's brain.
The spokesman said the findings were preliminary but indicated that local G4S guards had carried out the violent suppression of the protest. PNG police and local villagers did not appear to be involved, he said.
But nobody was being ruled out, he stressed, as investigations were continuing.
The spokesman said that G4S management in the centre had stood down all the local security guards. The police had been forced to get them back to the centre for interviews, he said.
Those who came from outside Manus Island were currently prohibited from going home. The spokesman could not say whether they were currently working in the centre.
Deputy police commissioner Simon Kauba told Fairfax Media: "The investigation is ongoing. We've employed people in Port Moresby and Manus."
The police had begun interviewing local G4S workers on Monday and were still carrying out the interviews, the spokesman said.
Mr Kauba said about seven or eight officers were investigating "on the ground" and he expected the case to "take all week".
The police spokesman said reports had been submitted by the local police chief Alex N'Drasal on the events.
"Mobile squad" police officers were providing written statements and also being interviewed, the spokesman said.
But initial reports suggested they had not been involved in the violence.
Warning shots had been fired, the police spokesman said. These had likely calmed the situation, he said. "Otherwise, the place would have been burnt to the ground."
There was confusion about the help being given by Australians. Mr Kauba said Australian assistance was "not necessary" and had not been requested.
But a spokeswoman for the AFP said the Royal Papuan New Guinea Constabulary (RPNGC) had asked for help with "the coronial of the deceased Iranian being conducted by the PNG authorities".
The spokeswoman said two Victorian Institute of Forensic Medicine officers would travel to Port Moresby to support the PNG coroner with the post-mortem examination.
The local PNG Post Courier reported that Mr Kauba had said that locals and PNG police had been "cleared" of the investigation.
In Parliament meanwhile, the House of Representatives passed a motion admonishing shadow defence minister Stephen Conroy for accusing Lieutenant-General Angus Campbell, the head of the government's Operation Sovereign Borders, of being engaged in a political cover-up following the death.
Foreign Minister Julie Bishop demanded that Labor leader Bill Shorten sack Senator Conory, describing him as "this dog of war", but Mr Shorten said the senator's withdrawal of the remark spoke for itself.
Tasmanian independent Andrew Wilkie, a former classmate of General Campbell, moved the motion, saying: "I think a line was crossed yesterday when the Opposition defence spokesperson called into question the integrity of General Campbell".
Senator Conroy defended himself, saying: "We've seen tragic circumstances arising on Manus Island as a result of the Government's actions and there needs to be a full account.