At least 30 people have died since the start of May in one camp for displaced civilians in northeastern Congo, a death rate that camp officials said was unprecedented, with some confirmed to have died from Ebola in a sign the disease could be spreading fast there.

It was not possible to confirm the causes of all the deaths because patients or their relatives in Kigonze camp in Bunia – the epicentre of the Ebola ‌outbreak in Democratic Republic of Congo – had until Thursday refused testing, a camp spokesperson and aid organisation Caritas said.

However, all had symptoms including headaches, fever and vomiting, which are associated with Ebola, a camp spokesperson, a bereaved father, three aid sources and a civil society leader told Reuters.

“People didn’t just die like this before,” camp spokesperson Desire Grodya Bapi said. The deaths in Kigonze, which has more than 15,000 residents, raise fears that Ebola may be circulating undetected among eastern Congo’s over 5 million displaced people, with resistance to testing compounding the challenge posed by severely limited sanitation measures.

Camp president Dz’djo Ndrutsi Etienne said 10 people were buried this week alone. Grodya said the camp typically recorded between one and three deaths per month.