South Africa has now released all but one of 145 Namibians who were kept without trial in an internment camp for more than six years, it was announced in the territory's capital of Windhoek yesterday.

South African administrator general in Namibia, Willem van Niekerk, said 74 internees had been freed in the northern town of Oshakati, following the release of 54 last May and others earlier this year.

He said they had been freed because a board of inquiry had found that they "no longer constitute a threat to law and order."

Van Niekerk did not name the person still being kept prisoner, nor did he say where he was. His chief aide, Sean Cleary, said no futher details would be given, but an official said later that the individual was being held because "he still constitutes a security threat."

The 145 prisoners, including a number of women, were captured when South African troops crossed the Angolan border in 1978 and attacked a camp of the Namibian guerrilla movement, the South West Africa People's Organization (SWAPO), near Cassinga.

Between 800 and 1,000 men, women and children were reportedly killed in the raid, which the Pretoria government said was on a key guerrilla base.

The captured people were taken to an internment camp at Mariental, south of Windhoek, where they were kept under a regulation permitting indefinite detention without trial.

They swept into the news last spring when the South African government issued a decree banning an American-sponsored court action to free some of the internees.

Before the case could be brought to court, Justice Minister Jakobus Coetsee invoked an obscure section of South Africa's Defense Act to prevent it from being heard "in the national interest."