British and Hong Kong officials are scrambling to get more information on 2,800 boat people whose backgrounds have been queried by Vietnam.
The number represents a huge chunk of the 7,000 or so Vietnamese in Hong Kong camps who have yet to be cleared for return.
The larger-than-expected figure emerged during discussions between British minister with special responsibility for Hong Kong Jeremy Hanley and senior Vietnamese Foreign Ministry officials.
Mr Hanley launched a humanitarian plea for Vietnam to take every boatperson before the handover - regardless of nationality.
Anyone not taken by Hanoi and left in Hong Kong at the handover faces statelessness. Last week Hong Kong was forced to free 217 boat people rejected by Hanoi.
'We don't yet have agreement on the issue of those rejected, but Vietnam has told us they will give it a full review, that they will look at everything again,' Mr Hanley said.