Twelve food samples have been found to contain non-permitted preservatives, heavy metals, drugs and bacteria in Centre for Food Safety tests.

It tested 6,100 food samples last month with an overall satisfactory rate of 99.8%. However, two fresh beef samples contained preservative sulphur dioxide, while a cooked chicken and a chicken noodle sample were contaminated with Staphylococcus aureus.

A frozen swordfish sample contained mercury exceeding the legal limit while a frozen shrimp contained metabolites of antibiotic nitrofuran.

The six other items were a noodlefish, chilli radish, chilli bamboo shoot, bamboo shoot, leaf mustard and dried fig.

The centre has asked vendors to stop selling the affected food and issued warning letters.