South Korea's food watchdog has detected quantities of melamine, an industrial chemical, in chocolate products from foodstuff giants Nestle SA, Mars Inc. and South Korea's Lotte that were manufactured in China, Yonhap News reported Saturday.

The Korea Food and Drug Administration (KFDA) said 2.38 parts per million (ppm) and 1.78 ppm of the toxic substance was discovered in samples of M&M's Milk and Peanut Snickers Fun Size products, respectively, from Mars Korea.

A Kit Kat bar from Nestle Korea was also found to contain 2.89 ppm of melamine, the agency said. The latest discoveries brought the number of locally tainted food items to 10 amid a broadening scandal over Chinese dairy products.

Melamine is a nitrogen-based chemical that can pose serious health risks if ingested frequently or in large quantities. It is used widely in kitchen utensils, but if added to food items the nitrogen can artificially increase protein levels, translating into higher prices.

Chinese health officials have said the use of melamine in dairy products has killed at least four infants and left 54,000 others ailing from kidney stones or other illnesses.

The KFDA is currently in the process of examining 428 processed foods manufactured in China to see whether they contain the hazardous substance. It has completed checking 288 products as of Saturday morning.