Ebola causes symptoms such as high fever, vomiting and diarrhoea as well as severe internal and external bleeding.
"For sure we are in the middle of an Ebola outbreak,'' Dumont told the Associated Press.
"But we cannot scientifically confirm the deaths are due to Ebola yet.''
He also said 42 people are suspected to have been infected with the virus, an increase from a previous count of 35 from the Congolese health ministry.
Dumont said MSF was currently monitoring 200 people who have been in contact with those infected, and Doctors Without Borders had set up an isolation unit where one person was recovering.
Last week, the Congolese health minister said laboratory tests had confirmed 11 deaths from the virus in the province, but it is unclear whether those people were included in Dumont's account.
On Tuesday the government of neighbouring Angola said it was closing part of its border with DR Congo to prevent the spread of the outbreak.
Ebola kills up to 90 per cent of the people it infects and is spread through direct contact with the blood or secretions of an infected person or with contaminated objects.
Last year, the Ebola virus killed at least 187 people in the same region of DR Congo.
An Ebola outbreak in 1995 killed at least 245 people in the village of Kikwit.