Fairfax Media said it understood the results of extensive tests on samples taken after the deaths - by Thai and international laboratories - were complete.
Authorities in Thailand previously said there was insufficient evidence to link the spate of mysterious tourist deaths in the northern city of Chiang Mai.
Ms Carter, 23, fell violently ill on February 3 while staying at the Downtown Inn in Chiang Mai and died a day later.
Her two New Zealand friends and travelling companions, Emma Langlands and Amanda Eliason, also fell ill but later recovered.
Four other foreigners and a Thai guide also died while staying in the popular tourist destination between January 11 and February 19 of this year.
A final decision on the cause of deaths and illnesses was expected to be made by the official information team after consultation with the eight-member panel of experts.
The Thai Public Health Ministry said the investigation was pursuing viral, toxin and chemical causes.
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