The childrens' deaths soon after receiving the common MMR vaccine prompted the government to temporarily call off vaccination programmes.
Lemalu Herman Retzlaff says post-mortems have been conducted, and a forensic pathology team from Australia is helping to establish why they died.
A separate police investigation is continuing.
Meanwhile, the health ministry has taken issue with some local and media speculation, saying it risks undermining the national immunisation programme.
Source:
RNZ Pacific