Fears that contaminated prawns were being sold in Singapore came to nothing yesterday after an investigation found that "gelatinous blobs" in the heads of prawns bought from a Sengkang market were, in fact, part of its heart structure.

A spokesman for the Agri-Food and Veterinary Authority (AVA), which had been probing a complaint from a customer, said: "It is normal anatomy and is prominent in fresh prawns. There are no food safety concerns, and the prawns are safe for consumption."

The AVA had looked into whether the sale weight of the crustaceans had been artificially increased with gelatin injections.

Reports of the practice are common in China.

The AVA spokesman added: "Food products that fail our inspections and tests will not be allowed for sale and enforcement action... will be taken."

Meanwhile, local fishmongers told The Straits Times that they buy their prawns from trusted suppliers and try to avoid those from China.

They said that their suppliers, mainly from Malaysia and Indonesia, conduct thorough checks on the prawns before selling the bulk to them.

"When the prawns arrive (at my stall), they are fresh," said Mr Toh Cheng Poi, 62, who works at the Lorong 1 Toa Payoh Block 127 wet market.

A fishmonger going by the name of Ah Kim, 68, has been selling raw seafood at the Toa Payoh wet market for more than a decade and is confident of the quality of her goods.

"We sell good and fresh prawns here," she affirmed in Mandarin.

A 40-year-old stall assistant, who wanted to be known only as Nelson, said: "If there is a problem with the prawns, they usually won't be let in (to Singapore). We could lose our jobs selling them.

"Incidents like these affect our earnings because customers feel scared for a while."

Stallholder Chia Fu Hai, 30, said he would not buy his stock from suppliers in China, because his current suppliers from Indonesia and Malaysia are more "trusted".

He is also baffled by the incident surrounding the so-called abnormal prawns.

"If suppliers inject every single prawn with gelatin just to bump up sales, I personally feel it is a waste of their time," said Mr Chia.

"If each prawn gets injected with one gram of gelatin, you will only get an additional one kilogram of weight after injecting a thousand prawns."