Hong Kong's Center for Food Safety Wednesday said nine meat samples were found with sulphur dioxide, a preservative forbidden in fresh, chilled or frozen meat.

Pork, beef and mutton samples were collected for tests in July and August from local fresh provision shops and meat stalls. Nine fresh beef samples contained sulphur dioxide.

The center has issued warning letters to the shop operators concerned and collected follow-up samples which passed tests.

Some traders use sulphur dioxide to make meat look fresher. However, people who are allergic to the preservative can fall ill from it. It is soluble in water and most of it can be removed through washing and cooking, according to a spokesman for the center.

The center warned consumers to buy meat from reliable market stalls or fresh provision shops. Do not buy or consume meat which is unnaturally red.