Dog owners have been warned to walk their pets on a lead when visiting beaches after strong winds left "toxic" shellfish stranded.
The Eastern Inshore Fisheries and Conservation Authority (EIFCA) said it was aware of "several mass strandings" of the animals in Norfolk and Suffolk.
It said some of the creatures may contain paralytic shellfish toxins (PST) that can be harmful if eaten.
In 2018 two dogs died after a suspected PST poisoning in Norfolk and Suffolk.
On Facebook, one user said shellfish had been stranded on the beach in Cromer, Norfolk.
The EIFCA said humans were also susceptible to PST with symptoms known to include:
- a tingling and/or burning sensation followed by numbness in the lips, tongue and face which progresses to extremities
- paralysis of limbs, loss of muscle co-ordination and a constrictive sensation in the throat
- other symptoms seen in dogs include vomiting, reduction in movement, difficulty walking and/or standing, and loss of consciousness
It said symptoms usually appeared within 30 minutes of consumption.
The EIFCA added: "If you suspect that your dog has consumed stranded fauna and is feeling unwell, please contact your local vet immediately".
Illnesses to nine dogs were reported over a two-week period in January 2018, and deaths were recorded at Holkham in Norfolk and Felixstowe Ferry in Suffolk.
A subsequent joint report by the EIFCA and the Centre for Environment, Fisheries and Aquaculture Science (Cefas) said the toxins found were typically associated with molluscs - mussels, clams, oysters and scallops - which washed up on the eastern beaches after winter storms.
As filter feeders, the molluscs absorb PSP toxins which are produced naturally by microscopic algae.