The department has called on locals to temporarily stop eating mandarin fish, even though the carcinogen only appears to be present in small amounts.

Fishmongers have also be asked to stop selling mandarin fish, under threat of lawsuit if they do not comply.

Hong Kong's Wenweipo newspaper reports the department tested 15 samples, each weighing one kilogram. They detected between 0.0022 and 2.3 milligrams of malachite green in 11 samples.

Guangdong Institute of Food Science and Technology Vice President Chen Yongquan said small amounts of malachite green are not harmful, even though regulations prohibit it from seafood.

A Hong Kong supermarket spokesman said the mandarin fish they sell comes from a registered fish market in south China's Guangdong province. The market has health and quarantine certificates, and supplies fish to Hong Kong.

An official with Huangsha market in Guangzhou said they hope the Hong Kong government finds the origin of the malachite green soon so innocent fisherman do not suffer any further economic losses. The industry has already suffered major losses this yeat, after contaminants were found in other products.

Nanfang Daily reports that mandarin fish are still selling well in many supermarkets and hotels in Guangzhou, the capital city of the Guangdong province. Guangzhou locals do not know the fish has been banned in Hong Kong due to contamination.

Malachite green contamination was detected in a number of freshwater fish last year, including common carp and mandarin fish. The Hong Kong government has released a list of fish markets that require government supervision to fish buyers.