An advocate for the people being held for Australia in Papua New Guinea and Nauru is concerned about the fate of men moved into a detention centre in Port Moresby.
Fifty-three asylum seekers not granted refugee status by PNG have been incarcerated at the Bomana centre, apparently indefinitely.
David Manne of Refugee Legal said there had been no reasons given for why this action had been taken.
Mr Manne provides legal representation for some in the group and said he had not been able to speak with his clients for some time.
"It is a matter of profound concern that they have been detained. Many of these men are experiencing very serious health conditions," Mr Manne said.
"The detention puts them at even further risk and is creating additional concerns of an acute nature about their medical treatment and their medical needs. It's a very dangerous situation."
Mr Manne and other refugee advocates have been speaking this week to an Australian Senate inquiry into government attempts to repeal the so called medevac law.
The law makes it easier for doctors to order the medical evacuation to Australia of refugees and asylum seekers held offshore.
Australia's Home Affairs Department told the inquiry the law, brought in by the opposition in March, was fostering self harm among people detained on the islands as a way out of detention.
But the Guardian reported a doctor implementing the medevac law had told the inquiry that there was "absolutely no evidence of an increase of self-harm behaviour since the implementation of the medevac bill".
Neela Janakiramanan, a Melbourne surgeon, said doctors had advised the government in May that a Liberal party win in the general election would further "destabilise the population of people who were overseas".
Between 1 March, when the law came into force, and the election in mid-May rates of self-harm were "extremely low", Dr Janakiramanan said.
An audit of 581 people in detention had found 97 percent had significant physical health issues and 91 percent had serious mental health issues, she said.
Mr Manne said the department's claim was baseless and that the law was vital if Australia was to meet its obligations to the people it detained.
"The critical issue here is that health care is best decided by those with medical expertise and not, as happened in the past before this law, by bureaucrats and politicians," he said.
"That's the focus and impact of the medevac law - to place into the hands of those with medical expertise the assessment about medical need."