SHANGHAI: Crab farmers in East China's Jiangsu Province hit out on Friday against claims that their crustaceans could cause cancer.

Health officials in Taiwan Province reported that a carcinogen had been detected in hairy crabs raised in Yangcheng Lake, but the farmers insisted that their own investigation showed that the famous delicacy posed no health threat.

The crabs were bred under strict supervision and passed all tests before being sold to Taiwan, claimed the farmers.

However, Taiwan health officials said that nitrofuran, an antibiotic, had been detected in a batch of hairy crabs from Yangcheng Lake.

The controversial cargo had been shipped to the island province by Jiangsu-based Kunshan Aquatic Product Co Ltd, which trades in crabs from 12 farms based at Yangcheng Lake.

The Oriental Morning Post newspaper reported that Taiwan's health authorities had impounded the crabs after a total of 3,000 kilograms of the crustaceans were found to contain the antibiotic on Wednesday.

The crab farmers insist that it remains unclear whether the animals were actually from Yangcheng Lake, adding that the antibiotic may have been added to the crabs while they were in transit.

Yang Weilong, chairman of Suzhou Yangcheng Lake Hairy Crab, one of the affected companies, invited the media and Taiwan health officials to visit Yangcheng Lake. "They can catch any crab in the fresh water and take their own tests," he stressed.

"We will take full responsibility if problems are found in our crabs. If not, they should take the responsibility."

In a statement on its website, the Kunshan municipal government stressed that officials on both sides of the Taiwan Straits should work to get to the bottom of this case.

Crab breeding is an important industry for this famous lake, which is expected to yield 2,000 tons of hairy crabs this year. Around 10 per cent of this is expected to be sold to markets including Hong Kong, Taiwan and Malaysia.

Yang said the association has strengthened its checks on all hairy crab producers and overseas dealers to safeguard the quality of the crustaceans.

Taiwan media reported that consumption of hairy crabs has dropped sharply in the island province. But the influence on the mainland has not been so marked.

"I haven't seen any decline in the number of diners who come to eat hairy crabs," said Judy Zhang, a spokeswoman for the Shanghai Central Hotel, which is famed for its crab feasts.

Food authorities in areas including Shanghai and Guangdong Province have stepped up their inspections of hairy crabs.

Fisheries experts called on the public not to overreact to the incident, pointing out that the mainland has implemented strict regulations on the raising of crabs for many years.