Doctors scoured remote villages in eastern Congo on Thursday for people infected with plague after an outbreak in a diamond mining town that has killed at least 61 miners and infected 400 people.

An aid agency said on Thursday it had found an infected person in a village 115 km (72 miles) west of Zobia, where the plague was first detected, and U.N. health workers said they had heard reports of more new cases in the mining town.

Pneumonic plague, which is highly contagious, broke out two months ago in Zobia, a town that was home to at least 7,000 diamond miners, some 300 km (186 miles) north of provincial capital Kisangani.

“There is one case of someone who had the plague and arrived in Buta from Zobia,” Philippe Havet, emergency coordinator for Medecins Sans Frontieres, told Reuters. “But he had already been treated so there is no danger of him spreading the plague.”

Luc Kishabongo, World Health Organisation (WHO) representative in Kisangani, told Reuters a local doctor in Zobia had called him on Thursday to say there were more cases of plague coming in but there were no more details.

Doctors also fear the disease may have spread when 4,000 of the miners evacuated Zobia and disappeared into the bush last week. They fled to avoid catching the plague but also to escape clashes involving various factions of the security forces guarding the mining area, Havet said.

Zobia is in the volatile Ituri region, where ethnic militias still roam, terrorising communities even now after the end of Congo’s wider war, which was declared over in 2003.

“Our teams are searching villages in between Zobia and Buta to try and see if there are people who fled Zobia while infected,” Havet said. “People are very worried as they saw how infectious this disease is and how it kills in three days.”

Working with two teams on the ground, MSF is trying to locate infected miners so that they can be taken to health centres where they would be isolated and treated, Havet said.

Kisangani is a major trading centre on the Congo River and health officials fear fleeing miners might carry the plague to Congo’s third largest city.

So far, none have been found by a WHO team dispatched to Kisangani with supplies of antibiotics to stem the outbreak and ensure that health workers in the region isolate suspect cases.

The WHO team has security clearance to go into the lawless Ituri district on Friday and hopes to find out whether the disease is still spreading.

Congo is struggling to recover from a five-year war that sucked in six neighbouring countries and divided Africa’s third largest nation. Although officially over, residual violence kills 1,000 people every day, mostly from hunger and disease, an international aid agency said last year.