The documents, obtained under freedom-of-information laws from the Department of Immigration, reveal that amid the panic security guards left their posts, communications broke down, there was no official chain of command and no emergency response plan was made for an outside threat. They also show that, after reports of guns being drawn, only expats were ordered to be evacuated, without the knowledge of the G4S security officers. Mr Morrison declined to comment on the matter. The documents that show what happened in the fight have been heavily redacted on the grounds they would damage relations with the PNG government and contribute to a ''lessening of confidence'' in the Abbott government, which had been in power for six weeks when the trouble flared. In the dozens of pages of documents are incident reports that firearms were drawn, a team of 20 Incident Response Team officers were mobilised and security was afraid the centre could be breached. A media release from the office of Mr Morrison two days after the fight tried to quash reports that firearms had been drawn, saying it ''appeared to be without basis'' and the army were ''carrying sticks and rocks''. But the internal documents released to Fairfax Media, apart from the media release, make no mention of ''sticks and rocks''. A departmental spokesman said Mr Morrison had been briefed and that was part of the information that was redacted.

An email from the director of operations of G4S Immigration Services questioned why the reference to firearms had been removed and whether it was ''intentionally omitted'' from a report. The G4S response was that ''firearms were not used to defuse the situation'' and that was regarded as confirmation that firearms had not been drawn, the Immigration spokesman said. The use of guns was mentioned in an Amnesty International report on Manus Island released last month in which asylum seekers were quoted as saying they heard two shots fired. ''This goes beyond the culture of secrecy, it would appear that it is in the realms of a cover-up,'' opposition immigration spokesman Richard Marles said. ''This is not about preventing the release of information for operational reasons, it is about preventing the release of information because it does not suit the government. What is absolutely clear is that the Australians felt their security was compromised and that makes it a matter of public interest to Australians.'' Greens senator Sarah Hanson-Young said Mr Morrison's claims that this was a matter for the PNG government were not sufficient. ''This is an Australian taxpayer-funded detention centre and the public have the right to know what is going on,'' she said.

"When Parliament resumes I will be moving for an independent inquiry into the incident.'' The Immigration Department documents also reveal that a draft media statement was expected to cause problems, with one aide told not to take ''offence or get angry'' when they saw the proposed statement. A G4S post-incident debrief document revealed serious deficiencies in the risk management of the centre, issues with high-level command and control, and that no emergency response plan was in place for the ''threat of breach from outside inwards''. It said G4S staff were taking orders from others, that there was no chain of command and not enough hand-held radios, which were analog and did not work properly. The conduct of some G4S staff was also an issue. ''Calm, controlled, concise direction and positive body language is very important to ensure that other staff and the transferees feel safe and secure and unnecessary angst is not created,'' the debrief said.

The department said communication has since been strengthened, additional radios have been provided and staff were receiving incident response and refresher training. Internal emails exchanged after the clash reveal G4S staff knew the incident was going to be a problem: ''This is going to hurt [redacted] real bad.''