A patient in Liberia has tested positive for Ebola more than two weeks after the last case was discharged, senior officials say.
Liberia had the most deaths in the world's largest Ebola outbreak, but has not had a case for more than two weeks and was counting down to being declared Ebola-free.
But Francis Kateh, the acting head of the country's Ebola Incident Management Team, said a test has come back positive for a female patient in the capital Monrovia. A second test is generally done to confirm the diagnosis.
Tolbert Nyenswah, who runs Liberia's Ebola response, said he had been told a person had tested positive. He said the patient has been transferred to a treatment centre in Monrovia.
Dr Kateh said: "It is confirmed, we've got the first test and it is confirmed."
In a worrying sign, it is not clear where the woman became infected. She doesn't seem to be linked to any of the people on a list of contacts of other Ebola patients, he added.
"We have to investigate where the person came from. Did they travel out of the country?"
An emergency meeting will be held tomorrow to compile data on the case.
Countries must wait 42 days from when the last patient tests negative to be declared free of the virus.
The west African outbreak has killed more than 10,000 people