A post-mortem on the body of the 23-year-old Iranian asylum-seeker killed during violent clashes on Manus Island still has not been carried out eight days after the man died, a Senate estimates hearing has been told.

Immigration Department Secretary Martin Bowles told the hearing in Canberra on Tuesday that Reza Barati's body had been flown to the Papua New Guinean capital Port Moresby but indicated it had not yet been examined.

"As of today, my understanding is still that the deceased has been moved to Port Moresby in anticipation of an autopsy," he said.

Both the PNG and Australian governments have said that a PNG police investigation is under way into Mr Barati's death.

Fairfax Media reported last week that his body was being minded by employees of security contract G4S who are due to end their contract on Friday.

Mr Bowles also revealed gas canisters were fired in the incident.

"G4S [was] drawing back to protect the internal perimeters ... that's when they discharged a gas canister and warning shots were fired ... I will stress that this is still to be tested," Mr Bowles said.

Mr Bowles said he received a phone call at roughly 1am about the violence on Monday night. He told the hearing he learnt of G4S's involvement through G4S staff on the island.

It was not until Saturday night that he learnt the violence occurred inside the centre, he said.

As of Saturday, Transfield Services will take full control of the centre.

A spokesman told Fairfax Media that the company would continue to employ local security forces, despite their implication in the violence.

With Sarah Whyte

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