Food officials were still trying to establish last night whether Hong Kong has imported contaminated string beans blamed for poisoning more than 80 people across the border. The retail price of string beans fell up to 40 per cent from the usual $8 to $10 a catty to $6 in local markets yesterday as news of the poisonings spread. Even with the big price cut, vendors said people were reluctant to buy. Sichuan-style, dry-fried string beans is one of the most popular local dishes, according to food critic Lau Kin-wai. The food poisoning scare follows reports of an increasing number of cases in the mainland media. A Guangzhou Daily report yesterday said 84 people from five factories in Longgang, Shenzhen, suffered symptoms including dizziness and vomiting after eating string beans on March 24. In Hong Kong, the Food and Environmental Hygiene Department said it had stepped up inspections and tried to contact mainland authorities to determine whether the contaminated beans had been exported to the city. The department said it had received no reports of food poisoning so far. 'All vegetables imported from the mainland came from registered farms,' a department spokesman said. However, it remained uncertain whether the contaminated beans were sold in local markets. Edward Lai Kwok-yan, general manager of the Vegetable Marketing Organisation, warned that people should soak string beans in salted water for at least 30 minutes to dilute any residual pesticides before cooking. Mr Lai also said thoroughly cooking any vegetable would make it safe for consumption. But he believed that the contaminated beans were not sold in Hong Kong. A vendor at Kam Hing vegetable stall in North Point said many customers hesitated to buy string beans yesterday, even at only $6 a catty. 'I made a lot of effort to explain that our string beans came from registered farms in the mainland, which were different batches from the ones that caused the food poisoning in Shenzhen,' she said. But people chose to buy snow peas instead, she said, with sales doubling. Another North Point vegetable stall owner said he had cut the price from $10 a catty to $6. Housewife May Chan said she would not buy string beans until the scare was over. 'There are still a lot of other choices. It is unnecessary to put my family's health at risk by eating the beans at this moment,' she said.