Health officials are attempting to reach 125 people thought to be linked to the 19 suspected of having contracted Ebola. Three people have died so far.
The World Health Organisation (WHO) on Sunday confirmed a second case of Ebola virus in the Democratic Republic of Congo after an outbreak of 17 other suspected cases of the deadly disease.
National officials and the media agency announced on Friday that at least one case of the virus had been confirmed in the village of Lakiti.
Three out of 19 suspected and confirmed Ebola cases have died so far, Eugene Kabambi, WHO's Congo spokesman, said.
It was not immediately clear how the first victim, a deceased male, caught the virus, although past outbreaks have been linked to contact with infected bush meat such as primates.
Health officials are trying to trace 125 people thought to be linked to the cases identified in the remote northeastern province of Bas-Uele, near the border with the Central African Republic, Kabambi said.
Experts say to prevent the spread of the virus they must quickly track down, test, isolate and treat suspected cases.
They also need to protect health workers and educate the population about hygiene measures.
The worst outbreak of Ebola killed more than 11,300 people in the West African countries of Guinea, Sierra Leone and Liberia, and infected more than 28,000. It peaked in late 2014, causing global alarm, but active virus transmission ended last year.
The latest Ebola outbreak is Congo's eighth, the most of any country. The deadly haemorhagic fever was first detected in its dense tropical forests in 1976 and named after the nearby river Ebola.
That experience helped Congolese authorities respond effectively to an outbreak in 2014 that killed dozens of people.
The GAVI global vaccine alliance said on Friday some 300,000 emergency doses of an Ebola vaccine developed by Merck could be available in case of a large-scale outbreak and that it stood ready to support the Congo government on the matter.