The Latest on the deaths of an American and a Swedish investigator for the United Nations in Congo (all times local):

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7:10 p.m.

The United States has issued a travel warning for Congo.

A State Department statement warns of unnecessary travel there, citing "ongoing instability and sporadic violence" in many areas.

The warning comes a day after Congo confirmed the deaths of an American and a Swedish expert for the United Nations and their interpreter. Their bodies were found in a shallow grave Monday after the team disappeared more than two weeks ago while looking into recent alleged rights abuses.

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6:35 p.m.

Congo's government says it will investigate the deaths of an American and a Swedish expert for the United Nations and their interpreter. Their bodies were found in a shallow grave Monday after the team disappeared more than two weeks ago.

Meanwhile, Sweden says it is opening a murder investigation.

American Michael Sharp, Swedish national Zaida Catalan and their interpreter Betu Tshintela went missing March 12 along with driver Isaac Kabuayi and two motorbike drivers in Central Kasai province. They were looking into alleged human rights violations by the Congolese army and local militia groups.

The U.N. secretary-general says the world body will conduct an inquiry into the deaths.