SEVENTEEN asylum-seeker children suspected of being trafficked from Vietnam have vanished from immigration centres across the country, and authorities admit they have not been searching for them.

The boys, mainly Catholics from the north of Vietnam, arrived by boat on Christmas Island between June 2010 and May last year. But despite most of them being missing for months, an investigation by The Sun-Herald has revealed police have not been searching for the children and the Vietnamese embassy in Canberra has been kept in the dark about their disappearance.

An embassy official said it had been unaware the children were missing. ''We have now asked them to investigate and tell us what was happening. We have still heard nothing.''

Before the boys, the youngest of whom is said to be 15, disappeared they told advocates their parents had been tricked into giving them into the custody of an older Vietnamese man promising them work and education in Australia.