Hong Kong’s Centre for Food Safety has found illegal levels of mercury in fish on sale at three Japanese restaurants in Tsuen Wan, Shatin and Tsim Sha Tsui. The restaurants were found to be selling tuna sashimi that exceeded the legal limit for mercury of 0.5 parts per million, according to a government release.

A branch of the Sushi Express chain in Tsuen Fat Building in Tsuen Wan contained mercury at 1.6 ppm, Apple Daily reported. Sushi Express, a company from Taiwan with at least 16 restaurants and 35 take-away outlets in Hong Kong, is popular for its low-priced sushi products.

A sample of tuna from Flame Japanese Cuisine in Wah Fung Building in Tsim Sha Tsui contained mercury levels of 1ppm, and others tested from Sushi Tokumi restaurant in Shatin, the New Territories, contained mercury at 0.79 ppm.

All three restaurants have stopped selling the tuna products after being given warnings.

Mercury may affect the nervous system, particularly the developing brain. At high levels, mercury can affect fetal brain development, and affect vision, hearing, muscle co-ordination and memory in adults.