A Guangzhou court has ordered four people from Hunan to serve three to five years in jail for selling highly radioactive uranium ore that could be used in a nuclear bomb, a human rights group said yesterday. What's more, the 8kg of uranium ore, which has sickened more than 20 people, including the four defendants, is still missing, posing a serious threat to public health, the Hong Kong-based Information Centre for Human Rights and Democracy said. The men - Zhang Sangang , Yang Guoliang , Li Huibin and Li Zian - were sentenced on Monday, the centre said, without giving details of their prison terms. It said the uranium, which is enough to produce a nuclear bomb, may have been bought by Hong Kong or Macau buyers because the defendants claimed to have targeted overseas clients. In January, Guangzhou police arrested six people, including the four, after receiving reports from an informant who pretended to buy the ore. But police found only several grams of samples on one of the defendants, who all claimed that the rest was lost in a Ningyuan county hotel room by their partner in Hunan. Reports had said the four were farmers and miners and none had realised the danger. They used a plastic bag, a sack and carbon paper to pack the ore during their attempts to process, store, move and sell it. Yang even used a home sieve to 'refine' the uranium ore to raise its purity from 47 per cent to 56.7 per cent, after a buyer offered him 12.8 million yuan. A further five people who supplied the uranium to the four were also arrested in Hunan, the centre said. They were workers from the former state-owned 712 Uranium Mine, which provided the raw material for China's first nuclear bomb in the 1960s but was closed in 1985 due to poor mining standards. It was unclear how the five acquired the ore because Beijing has banned all unofficial uranium mining since the 1980s. The 712 mine was one of four key state-owned uranium mines in Hunan, where radiation has plagued thousands of workers and their relatives with a range of cancers, mainland media said.