Updated

A Congolese military official says a suspect has been arrested in connection with the deaths of an American and a Swedish investigator for the United Nations and their interpreter.

Maj. Gen. Joseph Ponde Isambwa made the announcement Friday.

The bodies of American Michael Sharp, Swedish national Zaida Catalan and interpreter Betu Tshintela were found late last month in Congo's Central Kasai province.

They had been looking into alleged human rights violations by the Congolese army and local militia groups. Three other local members of their team remain missing.

At least 400 civilians have been killed in the region since August amid a rebellion loyal to former traditional leader Kamwina Nsapu. The United Nations has said 23 mass graves have been found in the region, and at least 434,000 people have been displaced.