Three samples of freshwater grouper were found to contain trace amounts of malachite green in the latest round of tests on the chemical, the Centre for Food Safety says.

Three freshwater grouper samples contained trace amounts of malachite green, at levels of 0.014ppm, 0.15ppm and 0.25ppm. They were taken from three fish stalls at Tai Po Hui Market. The stalls will now stop selling the fish in question, while the centre traces the source.

As the levels detected were low, normal consumption should not pose any adverse health effects, the centre said.

Meanwhile, it called on the retailers to stop selling certain chocolate bars manufactured by Nestle Australia as they might contain pieces of plastic. Consumers are also advised not to eat them. The affected products are Kit Kat Caramel (65g) and Kit Kat Cookie Dough (65g) carrying best-before dates up to and including February 14, 2008.