Prime Minister Jacinda Ardern has asked for more detail about a 15-year-old boy who was sent back to New Zealand by Australia on a recent flight.
Australia's policy has already been described as "corrosive" by Ardern.
Ardern told told reporters after a Cabinet meeting this afternoon that she would expect "particular care" with a minor.
"Officials that have responsibility for dealing with cases that involve minors, as I understand are involved," Ardern said, but she wanted to "go back and look at the circumstances under which this deportation happened".
An Australian Home Afairs spokesperson contacted RNZ this evening to state officials didn't know when the boy had arrived, but that the minor hadn't been on last week's flight of 501s.
"The Department approaches visa cancellation of minors with a high degree of caution and consultation, to ensure all relevant factors are considered and the approach is consistent with community and Government expectations," a statement read.
"The Department complies with its legal obligations in circumstances where the removal of a minor is considered, including those under the Convention on the Rights of the Child.
"Non-citizens who do not hold a valid visa will be liable for detention and removal from Australia."
Regardless of their circumstances, the government has to make sure that if a young person is involved, they're being "dealt with appropriately", Ardern said.
Under the 501 policy "foreigners" can be deported from Australia if they're seen as a risk to the "health, safety or good order of the Australian community", are believed to be "not of good character", or have certain criminal convictions.
Successive New Zealand prime ministers have appealed to Australia, saying the policy unfairly sends Australian criminals back to New Zealand, a country with which they often have little to no personal connection.
Ardern said she "didn't agree" with Australian Home Affairs Minister Peter Dutton's comments that last week's 501 flight was a matter of "taking out the trash", and that extended to the broader policy.
"So actually, regardless of whether or not we're dealing with a minor, or whether or not we're dealing with someone who's older, I have a specific objection to the fact that we have people being deported from Australia who we consider to be Australians."
When asked if she had raised the point with Australian PM Scott Morrison, Adern said he knew her "position on the deportation policy".
In the event a minor was involved, she would expect that officials on this side of the Tasman would be informed.
"I don't get a breakdown every time there is a flight of 501s, I don't personally get a breakdown of the profile of those people being deported.
"But I would expect, and we have worked very hard to say to our Australian counterparts, even though we object to this policy, the least we can do is make sure we've got a protocol where we know where they're coming, we know what offences apply and we know the profile of those being deported," she said.
Ardern said it was too early to say definitively whether or not officials in New Zealand were informed, but the "specific agencies who deal with young people on the New Zealand side" know now.
It was an "issue that's been raised before" and New Zealand had "also raised its objections before," she said.
Oranga Tamariki has been "working extensively" with the relevant authorities on both sides of the Tasman.
The agency said the boy was in a managed isolation facility and receiving support while in quarantine.