People on the Isle of Man have been warned to be vigilant for Covid-19 symptoms after a person who initially tested negative later tested positive after leaving isolation.
Several people were now isolating as a "precaution", the government said.
Even fully vaccinated people should take action "immediately" if they develop symptoms, a spokesman said.
Three new cases have been identified in the past 24 hours, one of which was "locally acquired" from a known source.
The origins of a further case are "pending investigation", while the third is known to be travel-related.
The government is yet to clarify if any of the latest cases are connected to the case identified on Saturday.
It is not clear how long that person, who had travel history, had been out of isolation before becoming ill.
The government spokesman said the call for vigilance applied to everyone, "especially those who have a recent travel history" who may already have tested negative for the virus.
There are currently a total of 10 active cases on the island, all of which are in isolation.