Freetown (AFP) - A woman who died last week in northern Sierra Leone tested positive for Ebola, the National Ebola Response Centre (NERC) said Monday, in a setback for the country's bid to gain Ebola-free status.

There had been celebratory scenes last week when the country's last known Ebola patient was released from hospital in the central city of Makeni after being cured of the virus, raising hopes the west African nation may finally have beaten the devastating epidemic.

Sources contacted by AFP confirmed that the woman was in her mid-60s and lived in Sella Kafta village in Kambia District.

A swab taken after her death Friday confirmed she had contracted Ebola.

She had not travelled to either Liberia or Guinea, two other countries also blindsided by the worst outbreak of Ebola in history, which has killed some 11,300 people since first emerging in December 2013 in Guinea.

"We have sent a team from here to Sella Kafta village and we have already identified ten high-risk contacts that we are focusing on to stem any possible transmission," the NERC's communication director Sidi Yahya Tunis said in an interview with a local radio station.

"We have already isolated the high-risk contacts and are assessing whether the village will be isolated if need be," he added.

Tunis also said that a World Health Organization team which successfully tested an Ebola vaccine in Guinea that has been billed as possibly marking "the beginning of the end" of the virus would join NERC in Kambia to vaccinate contacts of the latest victim to "stop any possible train of transmission".

Tunis said people should "remain calm and not be frustrated over the development".

News of the new Ebola death came as a new school year got underway Monday, with measures in place to try prevent the spread of the virus.

Children's temperatures were being checked at many schools, and students were directed towards buckets of chlorine to wash their hands.

Schools were closed for more than eight months at the height of the Ebola outbreak.