Miguel de Serpa Soares told the General Assembly that a preliminary review of the information — from intelligence, security and defense archives and other sources — showed it could add to knowledge about "the context and surrounding events of 1961."
He said it could also add to knowledge about "the presence of foreign paramilitary and intelligence personnel in and around the Congo, and the capacity of armed forces present in and around the region at that time."
Serpa Soares was briefing the General Assembly on the interim report by former Tanzanian chief justice Mohamed Chande Othman, who has been reviewing new information on the crash of Hammarskjold's chartered DC-6.
Widely considered the U.N.'s most effective secretary-general, Hammarskjold, a Swedish diplomat, died when the plane went down near Ndola Airport in modern-day Zambia, then the British protectorate of Northern Rhodesia.
Congo won its freedom from Belgium in 1960 and Hammarskjold was flying into a war zone infested with mercenaries and riven by Cold War tensions. Foreign multinationals coveted its vast mineral wealth and the country was challenged by a Western-backed insurgency in Katanga province, which hosted mining interests belonging to the United States, Britain and Belgium.
In October 2017, Othman said in a report, "It is plausible that an external attack or threat may have been a cause of the crash." Serpa Soares noted that Othman asked nine countries — Belgium, Canada, France, Germany, Russia, South Africa, Sweden, the United Kingdom and the United States — to appoint "an independent and high-ranking official to conduct a dedicated internal review of their intelligence, security and defense archives to identify information that may be of relevance to the Dag Hammarskjold investigation."
He said seven countries took action following the request 11 months ago and new information was received from some officials as well as from other sources. There was no response from South Africa and the United Kingdom, he said.
In recent months, Serpa Soares said, Othman asked the African nations of Angola, Congo, Portugal, Zambia and Zimbabwe to appoint senior officials for similar reviews and has already received notification of appointments by Congo and Zimbabwe.
Serpa Soares stressed that "the active participation of member states remains of the highest importance in our shared search for the truth in this matter." Sweden's deputy U.N. ambassador, Irina Schoulgin, thanked countries that have appointed national investigators, stressing their importance "to drive the investigation forward." She strongly urged countries that haven't appointed an investigator "to do so without further delay."
"We owe it to the families of those who perished 57 years ago and to this organization itself" to review all records and archives, including those that remain classified, Schoulgin said.