The Centre for Food Safety has found excessive pesticide residue in a sample of choi sum and is following up on the case.
The sample was collected at the import level.
It contained chlorpyrifos at a level of 0.17 parts per million, 1.7 times the maximum residue limit.
Food safety officials said that based on this level, eating a normal amount of the vegetable is unlikely to cause adverse health effects.
Consumers are reminded to rinse and soak vegetables before eating them to reduce any pesticide on the surface.