The tension that broke into violent clashes a week ago, leaving 23-year-old Iranian Reza Berati dead on Manus Island, had been brewing for weeks, Mr Knight said.

''People were texting me saying 'it's going to blow up'. But [the detention centre's managers] tried to play it down.''

If his staff had been able to see the centre for themselves, Mr Knight says, he could have arranged extra police squads as a deterrent to the melee that erupted.

There are still conflicting reports of how things unfolded that night. But Immigration Minister Scott Morrison's admission late on Saturday that most or all of the violence happened within the centre perimeter - not outside, as he had previously suggested - bolsters witness accounts that locally-engaged staff of the security contractor that runs the centre, G4S, were responsible for much of the violence.

As best as the sequence of events can be pieced together, the tension soared after asylum seekers handed the centre managers a letter last weekend detailing their grievances, largely about the lack of information on their asylum claims. Some sources say that the asylum seekers were told they would not be given any help resettling in third countries.

On the Sunday afternoon, some asylum seekers began chanting in protest, feeling their concerns were being dismissed. That evening, about 35 broke out of the centre. They were quickly rounded up. There were arrests and injuries. Also that day, Mr Knight says, asylum seekers had intensified their verbal taunts against locally-employed guards, including threats to rape their mothers and sisters. This account has been backed up by other sources.

Workers at the centre have also said there were tensions between the detainees and local guards over supposed sexual relationships between asylum seekers and local women workers as well as anger among local guards over their meagre pay compared with the Australian guards.

When the simmering anger flared again the following night an unknown number are understood to have broken out of the centre. Those that did were quickly stopped by the notorious police ''mobile squad'', the subject of many previous accusations of beatings, rapes and murders in PNG.

They were chased back into the centre. While the police were clearly involved in the response to the riot - gunshots were fired, and they are the only protagonists who carry guns - both Mr Morrison's statement and one by G4S itself seem to put the spotlight on the security firm's workers.

There are other questions remaining. Mr Morrison has been unable to say categorically that non-protesting detainees were not caught up in the violence. Refugee advocates say that peaceful asylum seekers were yanked from their beds and beaten, though this has not been confirmed independently.

Mr Knight says there was also a fight among the asylum seekers themselves.

Tellingly, local employees were not working at the centre in recent days. As one worker said on Sunday, the situation highlighted the lingering tension between the detainees and the locals.