SEOUL - SOUTH Korea's food watchdog said on Tuesday that two more snacks imported from China were contaminated with the toxic chemical melamine, bringing the number of tainted brands discovered locally to six.

The products are Ritz Cracker Sandwiches Cheese, produced by Nabisco Food Suzhou Co, and Savory Rice Crackers from Danyang Day Bright Foods Co, said the Korea Food and Drug Administration.

Traces of melamine were previously detected in 'Misarang Custard' and 'Misarang Coconut' cakes, which were manufactured in China and sold by South Korea's Haitai Confectionery and Food Co.

The South Korean agency has been inspecting 428 brands of imported food. It has completed checks on 186 items and found six contaminated with the chemical.

All six brands have been recalled, it said.

South Korea began the inspection after China said melamine, largely used in making plastics, was found in infant milk formula, sickening nearly 53,000 children and killing four.

South Korea has banned the import of all products containing Chinese powdered milk.