The head of Australia's Immigration Department has blamed activists and "troublesome outsiders" for a looming and potentially violent standoff over the closure of the refugee processing centre on Manus Island.
Bureaucrats also confirmed Australia will pay up to $250 million a year in services for refugees and asylum seekers in Papua New Guinea even after the facility shuts and Australian personnel leave next week.
And authorities will also have to confront a last-ditch legal challenge - in PNG or Australia - to stop the centre being shuttered on October 31 and returned to the PNG defence force.
Officials confirmed water, food, power and sanitation will be cut off at "some point" next Tuesday, prompting Greens senator Nick McKim to accuse the government of trying to "starve" refugees out of the centre.
A defiant Mike Pezzullo???, secretary of the Department of Immigration and Border Protection, blamed the looming flashpoint on a "vigorous campaign" by activists to convince refugees they should remain at the processing centre.
The 606 people refusing to leave the facility reflected "attitudes that are being stoked and fuelled by troublesome outsiders who are encouraging these poor souls", Mr Pezzullo told the Senate estimates hearing.
He rejected assertions Australia was responsible for torturing refugees, and joked: "The only torture I'm aware of is sometimes when we have to appear here."
That drew a terse reply from Senator McKim: "I don't think torture is a laughing matter, Mr Pezzullo."
Asylum seekers have been offered alternative accommodation but one of the facilities, West Lorengau Haus, is still not ready - while another, Hillside Haus, consists largely of "transferable accommodation containers", the inquiry heard.
Australian Border Force deputy commissioner Mandy Newton also confessed she was "surprised" only two Manus refugees had responded to an offer to transfer to Australia's other refugee processing centre in Nauru.
"I thought there might have been further interest," she said.
Despite the centre's imminent closure, Australia will continue to foot the bill for food, services and healthcare under contractual arrangements that will eventually be handed over to PNG.
Ms Newton estimated the cost at $150 to $250 million for the 12-month period from November 1, although contracts were still being drawn up on Monday.
Even if the contracts are handed over to PNG, Australia will be financially liable because the agreement requires Australia to cover "all reasonable costs" associated with the refugees.
Barrister Greg Barns on Monday revealed lawyers in PNG would seek an injunction against the centre's closure, with paperwork to be brought in that country's courts this week.
They will argue the closure will result in an absence of safe and secure accommodation for refugees, Mr Barns told Fairfax Media, constituting a breach of their rights under PNG's constitution.
Human rights lawyer George Newhouse, working with Mr Barns, has also written to Immigration Minister Peter Dutton threatening to seek an injunction in Australian courts.
Meanwhile, the Immigration Department defended the imminent appointment of Australian engineering firm Canstruct, a Liberal Party donor, to run garrison, catering and security services for refugees in Nauru.
Canstruct will also take responsibility for some welfare services, and be empowered to use force against non-compliant refugees - despite having no direct experience in their of those areas.
"They'll have experience from day one when they start," Ms Newton said.
Canstruct was the only company interested in the job and was the only firm approached in a limited tender - a practice for which the department has previously been criticised by the auditor-general.