Both the United Nations and a Senate inquiry have failed in efforts to cast any light on the fate of 153 asylum seekers detained at sea by Australian authorities.

The Australian Government confirmed to the High Court earlier this week that the group, which set sail from India last month, was in custody on a Customs boat, but will not say where.

The Office of the High Commissioner for Human Rights issued an urgent appeal earlier this week for information about the group, which includes about 40 children.

It wants a full judicial review of how Australia is handling the asylum seekers in light of its obligations under international law.

Australia has responded to the United Nations in a statement, saying what is happening to the Tamils cannot be revealed as "all these matters are currently before the High Court of Australia".

It says: "the Australian Government will provide a full response once they are resolved."

There have also been attempts to grill the Commander of Operation Sovereign Borders, Lieutenant General Angus Campbell, during a Senate inquiry on Friday into the deadly February violence at the Manus Island detention centre.

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Greens Senator Sarah Hanson-Young deviated from the inquiry's regular line of questioning, asking: "Could you please tell this committee where the boat is?"

Lt Gen Campbell asked if this line of questioning was acceptable and was told by committee chair Penny Wright it was - and it came at his invitation.

"Indeed ... with respect, Lt Gen Campbell, your opening statement ... referred indeed to the Government's general policy about stopping boats, turning back boats, and the effectiveness of that from your point of view," Senator Wright said.

"So I think you have moved into those areas yourself."

The Government has given an undertaking in the High Court not to return the asylum seekers to Sri Lanka without three days' notice. Sri Lanka has indicated it will not take them back.

There was no answer from Lt Gen Campbell.

"That is a matter under consideration by [the] High Court, so it would not be appropriate for me to comment further, Senator," he said.

Senator Hanson-Young asked: "So you are refusing to tell the committee at this stage where the boat is? I just want that clarified."

Lt Gen Campbell replied: "No, I would not characterise it like that, Senator. I am indicating that because this matter is before the High Court it would not be appropriate to discuss it."

Lt Gen Campbell said he was unprepared for this line of questioning.

"You are asking a particular question that is not usual and not part of the invited script of these discussions," he said.

Lt Gen Campbell took a number of questions on notice or referred them to the Customs and Border Protection Service, but the Greens Senator wanted more from the head of the taskforce.

"Ultimately, the buck stops with you," she said.

Lt Gen Campbell replied: "Yes it does, Senator."

No Manus transfers since Barati's death: Government

Meanwhile, Immigration Department has revealed there have been no transfers to the Manus Island detention centre since the death of Iranian asylum seeker Reza Barati in February.

Deputy Secretary Mark Cormack told the inquiry that a halt has been called to allow the centre to get back on a more normal footing.

He said of the detainees currently being held, 306 have been interviewed to determine their refugee status and 65 have received initial assessments.

"Thirty-four of those have been negative and 31 positive. The next step for the 65 is that under the PNG legislation the minister for foreign affairs in the PNG government will confirm a final decision."

The inquiry also explored the circumstances surrounding the Manus Island riot.

The company that provides health services to the centre said up to nine asylum seekers have been removed from detention because of post-traumatic distress related to February's violence.

Regional medical director of International Health and Medical Services (IHMS), Dr Mark Parrish, told Senator Hanson-Young the distressed people are on the island, but not in centre.

Dr Parrish: "If we felt that there were particular things that we could not manage on Manus Island then we would make a recommendation for a particular individual to be managed elsewhere." Senator Hanson-Young: "And have you done that?" Dr Parrish: "For some cases, yes." Senator Hanson-Young: "And have all of those people been removed?" Dr Parrish: "Yes."

Dr Parrish said IHMS provides a high level of health care and that their response to the violence was "very good".

He said 69 people were treated during the violence.

The inquiry is continuing.