City’s market watchdog announced yesterday that eight groups of food products, including roast pork and rice cake, from 631 batches of samples taken from local markets failed food safety tests.

The problems include presence of e.coli and the total size of bacterial colonies. The samples tested covered 17 categories of food. Among the eight, three were processed grain products, two were edible agricultural products and other three were a meat product, instant food and frozen food. The market supervisor has ordered an investigation.