The person had also tested negative three times, but tested positive on Day 21 of quarantine, the government said.
But it said this case has a low risk of infecting others.
Health official Gaafar J. Uherbelau said the patient is isolated and contact tracing underway.
He said those who had been in contact with the patient, including travel companions, had been placed in quarantine.
So far close contacts who had been tested have returned negative results, Uherbelau said.
Additional contact tracing will continue, he said.