The Centre for Food Safety tested 13,300 food samples in November-December with an overall pass rate of 99.6%. Only 55 failed the tests.

The centre's Assistant Director Dr Miranda Lee said 37% were vegetables and fruit; 17% milk, milk products and frozen confections; 13% meat and poultry; 8% aquatic products; 5% cereals and grains; and, 20% other items.

Among the unsatisfactory cases Dr Lee said mercury levels of two samples of aquatic products alfonsino, a common fish used in sashimi, exceeded the permitted level.

Both samples were imported from Japan in December. They were found to have excessive levels of mercury. Dr Lee said occasional consumption would not harm health but consumption on a long-term basis could damage the neural system.

Alfonsino, a large predatory fish, is expensive and commonly used for sashimi. It, with swordfish and tuna, is regarded as high-risk food for containing heavy metals.

Dr Lee advised pregnant women and children not to eat large predatory fish.

The centre is tracing the sources of the unsatisfactory food.