Documents in which it is alleged that South African intelligence agents were involved in the 1961 death of UN secretary-general Dag Hammarskjöld have been found. Now, UN secretary-general Ban Ki-moon wants a fresh inquiry into claims that an apartheid-era South African paramilitary unit was involved in the assassination.Hammarskjöld died in an air crash in Zambia.Decades-old intelligence documents have been unearthed about the alleged plot, dubbed Operation Celeste.Copies of the documents were made public at the Truth and Reconciliation Commission 18 years ago but South Africa was unable to locate the originals, making it impossible to substantiate their authenticity.Pretoria has reportedly told the UN that the documents have been found and can be inspected.Ban's deputy spokesman, Farham Haq, told The Times: "The UN is aware that South Africa is conducting a search to see whether there are documents that might be relevant to the conditions and circumstances resulting in the tragic death of Dag Hammarskjöld and those who accompanied him."The secretary-general will report on progress made to the UN General Assembly, which will decide on further action, by the end of its current session.National Prosecuting Authority headShaun Abrahams said it had yet to receive a formal request for information from the UN."A formal process needs to be followed. [Then] we will be able to comment."Described as "the most notorious and perplexing cold case in the UN's history", Hammarskjöld and 15 others were killed in the plane crash during a peace mission in Africa.The Operation Celeste documents allegedly quote the director of the CIA as calling Hammarskjöld "troublesome" and saying he "should be removed".US media reports quote officials familiar with the case as saying the assassination was carried out by South Africa backed by the CIA, British intelligence and a Belgian mining company.The CIA has dismissed the claims as "absurd".A 2012 book, Who Killed Hammarskjöld?, led to the establishment of the Hammarskjöld Commission, with South African judge Richard Goldstone as one of its four members. He told ForeignPolicy.com that he had a "strong feeling" Hammarskjöld's death was not an accident.The commission's final report states: "There is persuasive evidence that the aircraft was subjected to some form of attack or threat as it circled to land at Ndola."- Additional reporting by Graeme Hosken..