The former secretary-general died when his plane crashed on September 17th or 18th 1961, near Ndola in Northern Rhodesia, now known as Zambia.
The cause of the crash has never been established.
Ban proposed appointing an eminent person to review documents and “communications” from various individuals before re-opening the inquiry.
Of particular interest is whether South Africa will be able to recover the original documents detailing a purported plot to kill Hammarskjöld code-named Operation Celeste.
The alleged plot came to light in 1998 when South Africa's truth and reconciliation commission received a file on the clandestine operation that may have involved a maritime research institute acting as a front for
A panel appointed by Ban last year was unable to conclude whether the “Operation Celeste” documents were authentic because it examined “poor quality copies”, Ban said in a report to the General Assembly.
That inquiry however said that there was enough information to pursue leads on whether the plane was shot down or the target of “other interference as a hypothesis of the possible cause of the crash.”
Ban said that if South Africa can provide the original documents, it may be possible to conduct forensic tests to determine whether they are fake.
“Whether the documents are authentic or not would allow the hypothesis relating to 'Operation Celeste' to be either supported or dispelled, either of which would be a contribution to the historical record,” Ban added.
In a letter included in Ban's report, South Africa offered its full support for the investigation and said it had ordered a search of documents and records concerning Hammarskjöld's death.
The eminent person tasked with reviewing the documents “would be in a position to determine the scope that any further inquiry or investigation should take,” said Ban.
The UN General Assembly in December 2014 adopted a resolution that called for a full investigation to finally shed light on the Swedish diplomat's death.