A group of Tamils was kept on-board the Customs ship Ocean Protector for a month last year as the Abbott government tried to convince India to accept the Sri Lankan natives back. The information about the group of 46 who left southern Vietnam has come via a Vietnamese asylum seeker currently inside a detention centre in Australia. Her nephew was on the intercepted boat. Some members of the Vietnamese community in Melbourne were aware of the group's plans to head to Australia by boat in March, Fairfax Media has learnt. According to information relayed to Australia this week, the adults who were taken back to Vietnam on HMAS Choules are being held at a detention centre in the province of Binh Thuan while a number of minors have been released. Separately, Anoop Sukumaran from the Asia Pacific Refugee Rights Network in Bangkok said he had received reports that the group were still in police custody but could not confirm the information they are being held in Binh Thuan.

"We have heard something similar," he told Fairfax Media. The group was handed over to Vietnamese officials in Vung Tau, about 100 kilometres south east of Ho Chi Minh City. Phan Thiet, the provincial capital of Binh Thuan, is more than 200 kilometres east of Ho Chi Minh. According to the state-run Bin Thuan Online, there is a "temporary police detention centre" in Phan Thiet. The publication boasted in August 2013 about how "ebullient and aggressive" youth had been "enlightened" by the centre's police superintendents before being released as part of a national amnesty. "Amid the joyful atmosphere of the nationwide amnesty under the State President's decision, the temporary detention centre of Binh Thuan Police solemnly held ceremony to announce amnesty decision to offenders who had good behaviors [sic] during the process of doing porridge," it states. Trong Doan, a Vietnamese Australian refugee advocate and former community leader, said it was no secret that detention centres and re-education camps were used across Vietnam to interrogate suspected political subversives.

He said it was likely that security officials would be sent to Binh Thuan from Hanoi, the Communist Party capital in the north of the country. "What usually happens is people are asked the same question again and again and again. If people are charged they will go to prison. The Communist Party runs the courts. They run everything, all the newspapers and all the NGOs," he said. Mr Doan said Vietnamese Australians were concerned at the secrecy that has surrounded the hand-back. "This type of secrecy is normally reserved for terrorism and national security not for a group of people who are tired and weak on a boat journey." Amnesty International has said that the asylum claims of the Vietnamese cannot have been adequately assessed and determined by government officials at sea. Mr Dutton, who publicly thanked the Vietnamese government on Thursday, said last year's High Court decision mean Australia was within its rights to screen people at sea and said he was satisfied those returned would not face state persecution.

"We can't trace people back through countries for the rest of their natural life – that hasn't happened under any program. But we assure ourselves of the fact that people aren't returning to persecution or to a difficult situation," he said. "We have worked with the Vietnamese in relation to this issue and I want to say thank you to the Vietnamese government for the constructive way in which they have been able to work with us. We have been able safely return those 46 people to Vietnam." Follow us on Twitter