China's top Communist Party leaders have sent police and health officials to investigate a mass poisoning Saturday near the eastern city of Nanjing. State-controlled media are now vague about the death toll, after initially reporting that 41 people have died and some 400 hospitalized.

The deadly incident occurred in Tangshan, an industrial center near Nanjing early Saturday. Customers, mostly laborers and school children, at a branch of the Hengshengyuan Soy Milk fast food chain began to collapse after eating fried dough sticks, sesame cakes and other traditional breakfast foods.

Official government newspapers Sunday reported that more than 200 people were rushed to the hospital and that "a number" of them had died. But on Saturday, the official Xinhua News Agency had reported that 400 people had been hospitalized and 41 killed. No official explanation has been given for the change.

China Central Television on Sunday broadcasted footage of ambulances and military vehicles speeding to the hospital, where dozens of victims were already being treated in crowded hallways and reception areas at 10 local hospitals.

It is not yet clear if the poisonings were intentional or due to spoiled food. Shopkeepers in the area said they were shocked by the outbreak.

One local man told Hong Kong Cable TV that the Hengshengyuan Soy Milk Shop had been around for a long time and had never had problems before. The shop has been shut down and its manager is being detained for questioning.

According to government statistics last year, 146 people were killed and more than 15,000 others were affected by food poisoning caused by rat poison, chemicals and bacteria.