Ma Jianzhong, head of Henan's health department, said the comprehensive study examined 280,476 villagers in 51,187 villages in the province who had taken part in illegal blood sales in the 1990s.

The health check found 25,036 HIV carriers and 11,815 Aids patients. The figures included 2,003 cases previously unknown to the authorities.

Illegal blood sales were rampant in the province in the 1990s when 'blood heads' persuaded cash-strapped villagers to sell blood on the black market.

The blood heads took the blood, extracted the valuable plasma and re-infused the villagers to prevent anaemia.

Many of the villagers became infected with diseases such as hepatitis B and Aids as a result.

Mr Ma said the month-long study, which involved the mobilisation of hundreds of thousands of cadres, was meant to establish the true picture of the infection.

Henan Party Secretary Li Keqiang said the study had provided valuable information on how to help victims.

'The most important thing is to find out the truth of the matter and to have a full picture of the condition of people who sold blood,' Mr Li said. 'It is only then possible to help. At the same time, it helps us in putting a stop to this chain of infection.'

He said the provincial government had put a lot of effort and resources into Aids prevention and more resources would be allocated.

In 2000, the provincial government spent 16 million yuan on Aids prevention. This year the figure rose to 200 million yuan with the support of the central and provincial governments, China News reported yesterday.

Aids activist Zhou Xingping, who has been working with Aids patients in Henan since 2001, questioned the accuracy of the figures.

He said the study would fail to give a full account because many villagers who sold blood had probably moved elsewhere.

'There are over 10 villages with serious Aids problems like Wenlou - where more than 1,000 of its 3,000 residents are HIV carriers. There is no doubt that the number of HIV carriers is more than the official figure,' Mr Zhou said.

Aids activist Hu Jia , who has just returned from Henan, estimated more than 1 million people in the province had the HIV virus.

'Aids and medical workers told us as many as 3 million people there have sold blood. If 30 per cent later become HIV carriers, then there should be at least 1 million HIV carriers,' he said.

'[The study] was an effort by the government to show that they have done a good job in combating Aids,' he said, 'But [by publishing such a low figure] they are trying to hide the iceberg below the surface and that is the real problem.'