The number of people taken to hospital in a massive food poisoning outbreak in Heyuan city, Guangdong, had risen to almost 500, a provincial health official said. The director of the supervision department of the Guangdong Health Bureau, Wen Weiqun, said most of the 484 patients had been discharged, with only about 60 still in hospital yesterday. Hundreds fell ill on Wednesday after eating pork and were admitted to four local hospitals, Xinhua reported, with the official toll of sufferers put at 400 yesterday. 'Some patients originally had problems such as high blood pressure and developed more serious symptoms after eating the poisonous pork,' Mr Wen said. 'That is why they have had to stay longer in hospital for observation.' But according to reports carried by the Web site of the official People's Daily, as many as 2,000 people had rushed to hospitals and clinics for medical checks after they heard about the outbreak. Mr Wen confirmed that the asthma drug clenbuterol had been found in the first pig offal sample that was tested while the department was still conducting analyses on others. The banned drug is often used by pig farmers to make pork lean. The Guangzhou Daily quoted Liu Qiwei, an investigator dispatched by the Heyuan city Government to the city's state-run slaughterhouse, as saying the tainted pork had been supplied by seven different pig farms in the city. Mr Wen said better co-operation between government departments was needed to curb the use of banned drugs in animal feed. 'Clenbuterol poisoning is not something new. We have had several outbreaks on a much smaller scale before,' he said. 'Different government departments need to co-operate. For example, we are responsible for supervising the quality of the meat after the animals were slaughtered. But the pigs were fed clenbuterol before they were killed.' He said departments in charge of husbandry, agriculture and commerce should co-operate in future crackdowns. It is understood Guangdong Vice-Governor Li Lanfang has arrived in Heyuan to head an investigation into the outbreak, the largest in Guangdong. In August, more than 100 people in Guangdong's Xinyi city suffered food poisoning after eating pork. The Guangzhou Daily said the prompt reaction by the Heyuan Government, which had sent officials from neighbourhood committees to warn residents not to eat pork, had helped to keep the outbreak under control. An official at the city's health bureau said the Government was considering prolonging the ban, which was due to be lifted today.