Smuggled pork appears to be behind a week-long food poisoning outbreak that has struck down 72 people - 15 of them in the past 24 hours. 'Meat coming from local slaughterhouses is strictly inspected and is safe to eat,' said Raymond Chung Kwai-ping, an adviser to the Hong Kong Livestock Association. 'We all agree contaminated internal organs are coming from an illegal source,' he said after meeting agriculture and food officials yesterday. All locally produced meat undergoes a safety inspection by the Food and Environmental Hygiene Department. Health Department officials believe the food poisoning is caused by clenbuterol, a drug used to make meat lean. Use of the drug is illegal in Hong Kong and farmers caught using it are subject to prosecution. Wong Kwong-wing, chairman of the Hong Kong Pig Farm Association, called for tighter legislation punishing such farmers. The Food and Environmental Hygiene Department continued inspecting meat vendors, checking about 500 in stores and market stalls. More than 350kg of pork and pig offal was surrendered by meat vendors unsure of the source, a department spokesman said. Most of the food poisoning victims bought the pig offal from markets in Tai Po and Sha Tin, and some from Yau Ma Tei and Tseung Kwan O. The Agriculture, Fisheries and Conservation Department said the contamination cases were still under investigation and promised closer monitoring of meat stalls. Four people remain in hospital in a stable condition.