Government and military officials have found the old immigration detention centre on Papua New Guinea's Manus Island to be very run-down.

Bushes have grown over some of the buildings and the floorboards are sagging.

The reconnaissance group's spokesman, Squadron Leader Alan Brown, also found termites and holes in walls.

"So far we've assessed the engineering logistics, medical and communication requirements," he said.

The group is looking at the best way of setting up asylum seeker processing centres in the short and long term.

They will also fly to Nauru to inspect the centre there, which is also reportedly run-down.

The Federal Government says it wants the centres up and running in weeks, not months.

But it will not know how much they will cost to fix until the reconnaissance group returns to Australia.

The team was dispatched after the Government's expert panel on asylum policy recommended centres on Manus Island and Nauru be re-opened.

Eight boats carrying a total of 454 people have arrived since the Government announced its new offshore processing policy on Monday.

Five of those boats came in a 24-hour period as the Government rushed its legislation through the Senate.

But Labor will not say what will happen to the recent arrivals, only repeating they run the risk of being transferred to an offshore processing country.

Opposition Leader Tony Abbott says he has little faith the latest asylum seekers to arrive will be sent offshore.

"What we are seeing here is obviously a determined effort by the people smugglers to test the resolve and the character of this government," Mr Abbott said.

"Now I've got to say the resolve of this government has been found wanting time and time again on this subject, so Julia Gillard is being put to the test.

"I hope she rises to the challenge, but based on what we've seen there's got to be a lot of doubt."

The Government says the surge in arrivals is not surprising, as people smugglers are trying to make as much money as possible.

Meanwhile the United Nations has warned the plan to re-open the centres could violate the human rights of asylum seekers.

UN officials say they are concerned about the psychological impact for those who would be affected.