AFP/ Freetown

Three more patients have tested positive for Ebola in a village in northern Sierra Leone already under quarantine after the death of a 67-year-old woman, authorities said on Tuesday.

The new cases -- bringing the total in a recent outbreak in Sellu Kafta in Kambia district to five -- were diagnosed on Monday, according to the National Ebola Response Centre (NERC).

Spokesman Sidi Yahya Tunis told reporters in the capital Freetown the three were among the 50 "high risk persons" identified as close relatives of the food trader, who died on August 28.

"The development remains a concern for us but since it has taken place within a quarantined home, it can be adequately monitored and further transmission can be contained," he added.

The outbreak brought to an abrupt end the optimism fuelled by the release of what had been Sierra Leone's last known Ebola patient from a hospital in the central city of Makeni in late August.

Sellu Kafta, a village of almost 1,000 people, was put under a three-week quarantine lockdown after officials announced a week ago that the woman had died after being sick for up to 10 days without the authorities' knowledge.

Local health officials said the experimental "Guinea ring vaccine" that has been administered by a World Health Organization team in the village since Friday was "progressing very well".

The three new cases were not among 116 people who have so far received the vaccine, according to the NERC.

Meanwhile officials say they are trying to trace a "high risk" niece of the woman who died.

"Let her come out and give herself up to the health authorities to be tested," Tunis said on state broadcaster Sierra Leone Radio.

"She should not think herself as a criminal but we want to test her as she had close contact with the dead trader. We are asking the community and family members to help in tracing her."

The west African outbreak of Ebola has killed some 11,300 people since first emerging in December 2013 in Guinea, with Liberia the hardest hit.