UPDATED 3.15pm: The riot on the Christmas Island detention centre is over.

Australian police retook control earlier this afternoon.

Riot police were deployed on the island this morning, taking back each building one at a time.

The detainees are now in a controlled compound.

Damage to the facility is being assessed.

LISTEN: Australian correspondent Donna Demaio speaks with Andrew Dickens

MORE: Government seeks information on Christmas Island riot

Complex legal issues are being cited as the reason why New Zealanders who want to leave Christmas Island could still be trapped there for weeks.

Immigration Minister Michael Woodhouse said Australia's promised him they're putting extra resources into it, but a long delay is still understandable.

"Each case is different, each case needs to be taken on its merits so I know as New Zealand's Minister of Immigration that some deportation files can be pretty complex and take quite a while to consider."

Australian authorities pulled out staff and sent in reinforcements last night.

Labour MP Kelvin Davis spoke to a couple of New Zealand detainees who have barricaded themselves in. He said the riot squad has just gone in.

"With batons and sounds like guns blazing, certainly tear gas canisters appear to be shot off. When I say guns, I think they're firing rubber pellets."

New Zealand detainee Lester Hohua sounded panicked when Newstalk ZB called him this morning, saying 'it's all happening. I can't talk right now.'

Davis thinks many of them will end up with broken bones by the end of the day and hopes no one will die.

"At the very least just get our people, our officials to check on the well being of the New Zealand citizens. They are going to need help after this is all over."

Australian Immigration Minister Peter Dutton confirmed reinforcements had arrived. Federal police may use rubber bullets to control detainees who refuse to follow instructions.

"They'll make judgments according to the operational needs and they'll respond to the threat according to their training and according to law," he said. 

"The Australian federal police response unit is a very professional one and they'll respond in the appropriate way."

But there are questions about why the official version of what's happening at Christmas Island is different from what detainees are reporting. 

Justice Minister Amy Adams is calling the Australian Immigration Minister this afternoon to get clarity.

"Certainly some of the media reports suggest that some of the experiences of detainees hasn't found that to be the case, so what we're being told officially we just want to ensure that this is exactly how this is being operationalised on the ground."

Kelvin Davis said we need to make sure the detainees have medical attention and legal representation.

Return of NZers from Christmas Island 'could take weeks'

The Prime Minister has confirmed it's thought New Zealanders were caught up in the riot at Christmas Island detention centre.

John Key said details are sketchy.

"We think it's likely that there may have been some New Zealanders involved, although I don't have official confirmation of that. We certainly don't have any advice that there are any injuries."

Key said it could take weeks for Kiwis on Christmas Island to return to New Zealand to fight their deportation from Australia.

He said, however, there is only one New Zealander there going through the paperwork at the moment, and getting back to New Zealand immediately isn't possible for a number of reasons.

"They may have been in prison for a long period of time and actually not have passports or travel documentation. If they are security risks to other passengers on the plane, because some of these people have a history of violence, then they won't be able to fly commercially."

The Australian Government has said it will pay for the charter flights if they're needed.

Labour calls for more pressure to be placed on Australian Government

Labour leader Andrew Little believes the Prime Minister should be on the phone to Malcolm Turnbull, telling him the Christmas Island riot has happened because people are being isolated from their families and support bases.

Prime Minister John Key has said it's a matter for the Australians to hand the treatment of people at Christmas Island, but New Zealand will give consular support to Kiwis who require it.

Little said Key should be asking the Australians what we can do to help, and as it is prisoners being treated inhumanely.

"Depriving them of their links to their communities and that the best hope we've got for them to get back on the straight and narrow, that's a hopeless approach," Little said.

"That's why the politicians who have the ability to make these decision. have got to act with a sense of compassion, to do the right thing and the popular thing."

Little said it's not good enough to say it's a problem for the Australian government.

"This is an issue that our government ought to be contacting relevant counterparts in Australia about, and saying what is happening there illustrates the very problem. They've got to change their approach to dealing with the situation they're in."

Australia's Immigration Minister Peter Dutton said authorities refuse to tolerate those who have damaged the detention centre.

"There's people that committed damage to Australian Government property to tax payers property ... they will face the full force of law in relation to that."

Australian authorities will investigate the death which sparked the riots.