Two oyster growers have temporarily stopped harvesting the molluscs after initial tests confirmed high level of toxins in the shellfish on Tasmania's east coast. They have to wait for further testing that will be carried out on July 11.

Health authorities have sent out a warning after an increased level of hazardous toxins were found in oysters from Norfolk Bay and the Great Oyster Bay area.

Stuart Heggie, state manager for environmental health at the Tasmanian Health Department, said there were no reports or incidents of paralytic toxins and the presence of the harmful substances was revealed during a routine testing.

Heggie added none of the toxic shellfish was sent to the market. But he was quick to note two oyster growers in the Great Oyster Bay area will have to stop their harvest until the level of toxins come down.

Regarding the symptoms after being infected with the fatalistic toxins, Stuart said, "Symptoms include a tingling in the mouth, you get pins and needles in your arms and legs and you can be a little unsteady, and a bit of nausea to go with it."

Echoing the opinion of Heggie with regard to suspending the harvest of the shellfish, Neil Stump from the Seafood Industry Council said, "They have to cease production and can't sell any product so it will impact directly on them." Stump further added, "Other growers in the adjacent areas, where we've also detected the presence of this algae, are on a watch and alert at this stage."

The Tasmanian oyster industry has seen several such setbacks. In 2013, the outbreak of Norovirus or an extremely contagious virus that can infect anyone led to 60 people falling ill after consuming oysters. Apart from that, the algal bloom in 2012 also had a negative effect on the oyster industry in the area.