Mr. Hammarskjold, a Swede, was killed with 15 others in the crash on the night of Sept. 17 to 18, 1961, in a forest in the British protectorate of Northern Rhodesia, an area that is now part of Zambia. Mr. Hammarskjold was on his way to broker a truce in the mineral-rich Katanga Province of what is now the Democratic Republic of the Congo. Mr. Hammarskjold was awarded the 1961 Nobel Peace Prize after his death.

There have been several investigations into the crash by both the United Nations and the authorities in the area where the plane went down.

The three-member panel, which Mr. Ban appointed in March after a request by the 193-member General Assembly, interviewed new witnesses who said they had seen two planes in the sky, one of which caught fire in the air before crashing into the bush. The panel also considered testimony from two former United States officials who said they had listened to or read radio intercepts that suggested that Mr. Hammarskjold’s plane had been attacked. The report also said that the provincial government in Katanga, aided by foreign troops, may have had “air capability.”

Mohamed Chande Othman, a Tanzanian prosecutor, led the panel, which included Kerryn Macaulay of Australia and Henrik Larsen of Denmark.

The report said the panel had spoken to, among others, four charcoal burners who were in the forest the night of the crash, as well as to Susan Williams, a British academic and the author of a book on the disaster, and Paul Abram, a former United States military official who had been monitoring several radio frequencies as part of his assignment at a National Security Agency listening post. Mr. Abram told the panel that he remembered hearing that the plane had been shot down by ground fire. The charcoal burners described slightly different memories of seeing two planes in the air and one of them catching fire.