The Niue government has confirmed Premier Dalton Tagelagi is a close contact of a Covid-19 case and is in isolation.
It follows the arrival of the first quarantine free flight with tourists from New Zealand on Monday local time.
Five people have tested positive so far.
Mandatory day three testing of the remaining passengers and all close contacts is being carried out today.
New Zealand-based public health expert Sir Colin Tukuitonga says the results of those tests are critical to Niue's health response as it will determine if the country is facing community transmission.
So far Covid-19 has only been detected at the border.
If the virus is detected in the community today the country will move to Alert level Red.
Niue's Director of Health has confirmed a man with pre-existing health conditions has been hospitalised with Covid-19 after arriving on the quarantine-free flight from New Zealand.