Fish checks: Centre for Food Safety Controller Dr Mak Sin-ping briefs the media, with the centre's senior chemist Lee Foo-wing.

Tests on six samples of Bombay duck fish have found no excess level of formaldehyde, Centre for Food Safety Controller Dr Mak Sin-ping says.

The amount of chemical found ranged from 30 to 137 milligrams per kilogram, well below the 400 miligram limit. She said there is no evidence to suggest anyone is adding the chemical to preserve the fish.

Dr Mak said as seafoods like shrimp and fish contain trimethylamine oxide, a natural chemical that releases formaldehyde and dimethylamine when decomposed, the centre also tested for dimethylamine.