It is one of the few countries in the world yet to have a confirmed case of Covid.
It comes after health officials in nearby American Samoa reported three people on board the Fesco Askold container ship had tested positive for the virus.
There are 17 crew members on the ship, local media report. In accordance with local regulations, all on board required a test before they would be allowed onto the island.
None of the crew have been allowed off the ship since and there are now moves to send it out to open waters.
