The U.N. General Assembly asked all members Thursday, particularly Britain, South Africa and the United States, to turn over any information they may have on the death of Secretary-General Dag Hammarskjold in 1961.
The U.N. chief died in a plane crash in Northern Rhodesia, now Zambia, on his way to try to broker a cease-fire in Katanga, a breakaway state in what is now the Democratic Republic of the Congo.
An independent investigation said in July that new information had emerged indicating that the crash might not have been an accident.
The new information includes reports from eyewitnesses who said they saw another plane in the air as Hammarskjold's jet approached the airport, and from others who said they thought his plane was on fire before it hit the ground.
The assembly also said two U.S. military officers either heard or read a transcript of radio transmissions from Hammarskjold's plane showing it might have been under attack.
The General Assembly called on any member to release any relevant records it has on the crash.