Home Affairs Minister Peter Dutton suggests DNA testing would be required to verify the Australian citizenship claims of Islamic State brides trapped in Syria.
However he argues it would be very difficult to see how the women and their children could be repatriated.
"There are some people who may claim to be Australian citizens - we don't know whether they are," Mr Dutton told 3AW Radio on Tuesday.
"You would need DNA testing and you'd need other checks to be made.
"But it is an incredibly dangerous situation and the government has been very clear that we aren't going to put defence personnel or DFAT personnel or home affairs personnel in harm's way to provide support to these people."
Mr Dutton said there was no question the return of Islamic State brides would expose Australia to an increased risk of terror.
"Some people will face arrest if they do get back to Australia because we've been able to gather enough evidence in relation to them," he said.
"Others we just don't know the level of threat.
"There are others who, on the advice from the agencies, pose a very significant threat. That is, there is a probability of them committing a terrorist offence if they return to Australia."
Prime Minister Scott Morrison has backed the minister's claim that it would be too dangerous for Australia to run a concerted effort to extract the women and children from Syria.
But he suggested Australia may be able to assist if they found themselves at borders and were confirmed to be citizens.
"Were people to find themselves at border points and things like that, well there would be a normal process that would be followed," he told 6PR Radio.
"But it would obviously be necessary to ensure that it was very clear about what any obligations Australia had at that time before going down that path."
Labor is not entirely satisfied with the Morrison government's argument that it is too risky to bring the women and children home.
Their families have pleaded with the federal government to help extract them from the al-Hawl camp.
Labor frontbencher Madeleine King said her colleagues would continue to pursue the issue throughout the week of Senate estimates hearings.
"I think this is a desperately grave situation that's happening in these camps," she told ABC radio.
"It is a very difficult decision for the government, what is being put to them, and I accept that.
"I accept it's a grave decision to have to think about and consider, putting other Australians' lives in peril to go into a very dangerous situation in foreign lands, so we will examine it further."
Meanwhile a survey has found most Australians are opposed to the repatriation of the Islamic State wives and children.
There are 20 Australian women and 46 children stranded in northern Syria following the defeat of ISIS.
Some 59 per cent of 1634 voters polled late last week were opposed to their return, The Australian reported on Tuesday.
Another 36 per cent of respondents were in favour.
Opposition to their return was strongest among coalition voters at 70 per cent, according to the Newspoll.
But Labor voters appeared to be split on the issue, with 50 per cent in favour of their repatriation and 45 per cent against.