The Centre for Food Safety (CFS) yesterday found malachite green, a cancer-causing substance, in two samples of turbot.

The samples, found in two stores at Pei Ho Street market in Shamshuipo, were found to contain 340 parts per billion and 480 parts per billion malachite green, the CFS said.

However, the CFS acting controller Ho Yuk-yin said the health risk by the substance would be minimal.

The CFS has tested five samples.

Ho said the centre would test the antibiotics levels of the samples and trace the origin.

He also said that the CFS would ensure that turbot fish are not sold in the market. "We will confiscate the product if we discover people selling it," he said.

Meanwhile, Beijing imposed a ban on the sale of turbot after detecting excessive amount of carcinogens in the fish.

A hotline has also been set up so that citizens can report sales of the contaminated fish, according to the municipal food security office.

Several other cities - including Tianjin, Xi'an - and Liaoning Province have also started quality inspections of turbot after that Shanghai announced last Friday it had detected excessive cancer-causing agents in turbot samples.

One of the stores in Pei Ho Street market was shut down.

A staff of the other store said they had stopped selling turbot fish and they were not aware of the problem.

Hong Kong Chamber of Seafood Merchants chairman Lee Choi-wah said all turbot fish had been imported from Shenzhen. He said the chamber would stop selling the fish until new test found the samples free from malachite green.

Hong Kong Federation of Restaurants and Related Trades president Simon Wong said the sales of other fish would go up by three to five per cent, which might lead to price increase.

Consumers said they would stop eating turbot.