Tests have confirmed an outbreak of the deadly Ebola virus in Congo, the World Health Organization (WHO) says.
Some 120 people died from Ebola in 2003 in the same area
Nine people have died and two more are sick in the Cuvette West province, scene of at least three Ebola outbreaks in recent years.
WHO Congo representative Amadou Yada said a family of hunters contracted the disease after picking up the body of a dead chimpanzee in the forest.
There is no known cure for the Ebola hemorrhagic fever.
Samples were sent to the International Medical Research Centre in neighbouring Gabon, which has confirmed that the deaths were caused by Ebola, Dr Yada said.
He said villagers in the Etoumbi district, some 700km north-west of the capital, Brazzaville, had gone to the forests to hunt elephants, when they came across the body of a dead chimpanzee, which they took home to eat, before becoming sick.
The BBC's Christian Tsoumou in Brazzaville says that most people in the forest area are hunters.
He says that after previous Ebola outbreaks in the area, the authorities have told people not to touch dead animals they find but few people take any notice.
Dr Yada said that a medical team was about to leave for Etoumbi to set up an isolation unit and warn people about the risks of touching dead animals and avoiding contact with those infected.
Ebola is highly contagious and is spread through body fluids, such as blood and sweat.
In 2003, 120 people died from Ebola in Cuvette West.