Officials in Guinea say a team of health workers and journalists who were trying to raise awareness about Ebola may have been kidnapped.
The team of six went missing after being attacked on Tuesday in a village near the southern city of Nzerekore.
Meanwhile, President Francois Hollande says France is setting up a military hospital in Guinea as part of its contribution to tackle the disease.
More than 2,600 people have now died from the Ebola outbreak in West Africa.
It is the world’s worst outbreak of the deadly disease, with officials warning that more than 20,000 people could ultimately be infected.
The UN Security Council is due to discuss the outbreak later on Thursday.
Last month, riots erupted in the area of Guinea where the health team went missing – near where the outbreak was first recorded – after rumours that medics who were disinfecting a market were contaminating people.
The three doctors and three journalists went missing on Tuesday after residents in the village of Wome pelted them with stones as they visited the village.
One of the journalists managed to escape and told reporters that she could hear the villagers looking for them while she was hiding.
The governor of Nzerekore told the BBC that the group were being held captive, although it remains unclear why.
A government delegation, including the health minister and the communications minister, has been dispatched to the region but the BBC’s Makeme Bamba, in the Guinean capital Conakry, says the delegation have been unable to reach the village by road because a main bridge has been destroyed.
The team is negotiating with local elders to try to gain access, she says.
There have been many reports of people in the region saying they do not believe Ebola exists, or refusing to cooperate with health authorities, fearing that a diagnosis means certain death.
Speaking on Thursday, President Francois Hollande said France was setting up a military hospital in Guinea as part of his country’s efforts to support the West African nations affected by the outbreak.
He said the hospital was a sign that France’s contribution was not just financial, adding that it would be in “the forests of Guinea, in the heart of the outbreak”.
The World Health Organisation said on Thursday that more than 700 new cases of Ebola have emerged in West Africa in just one week, showing that the outbreak is accelerating.
It said there had been more than 5,300 cases in total and that half of those were recorded in the past three weeks.
The epidemic has struck Liberia, Sierra Leone, Guinea, Nigeria and Senegal.
A three-day lockdown is starting in Sierra Leone at 00.00 GMT on Friday in a bid to stop the disease spreading.
Ebola virus disease (EVD)
- Symptoms include high fever, bleeding and central nervous system damage
- Spread by body fluids, such as blood and saliva
- Current outbreak has mortality rate of about 55%
- Incubation period is two to 21 days
- There is no proven vaccine or cure
Press divided on response to Ebola
Ebola: Mapping the outbreak
How bad can it get?
‘Biological war’: A week on the Ebola frontline
Have you been affected by the Ebola outbreak? You can send us your experiences by emailing [email protected]