GUANGZHOU - Disturbing amounts of some snack foods sold near primary and middle schools in Guangzhou failed recent tests for food quality, the city's administration of industry and commerce reported on Monday.

About 50 percent of the ready-to-eat, non-fermented bean products and 68 percent of the preserved fruits tested failed quality tests for excessive bacteria and coloring or flavoring agents, the city said.

The tests were made last year on 234 samples of snacks made by 193 enterprises and sold near schools. A total of 213 of the samples, or 91 percent, passed the tests.

Tests of many products, including seed and nut products, instant noodles, cooked meat, ready-to-eat seafood products, biscuits, pickles, candy, and chocolates, showed no contamination.

Excessive bacteria in non-fermented bean foods may be attributed to contamination of the raw materials, manufacturing equipment, workers, production environment, or packaging, the city said. Contamination during transport and poor storage conditions were also cited as possible causes.

Of samples failing the tests, particularly preserved fruits, most were found to have excessive saccharin sodium and sodium cyclamate, which are used to sweeten the food but are harmful to health if consumed in excess. Excessive artificial coloring agents found in the substandard foods included carmine, tartrazine and sunset yellow.

The city has pulled the contaminated foods from the shelves and has advised consumers to check the packaging, expiration date, and storage requirements of food and to avoid suspiciously colored food.