Further tests have confirmed earlier findings that dogs died or became sick on north Norfolk beaches over the New Year period because of a neurotoxin found in shellfish.

Last month scientists at the Centre for Environment, Fisheries and Aquaculture Science (Cefas) analysed samples of fish and starfish from Cley beach where Julie Thomas' dog, Hattie, died within an hour of eating a fish on December 31.

Researchers reported finding 'paralytic shellfish poisoning (PSP) toxins in the starfish samples', and added it showed 'a potential route of intoxication'.

Further tests at the marine science institute were carried out after a Siberian husky died in Felixstowe on January 13 after eating fish on the beach, and these have confirmed the previous findings. Researchers said tests on starfish samples found at the Suffolk town revealed extremely high levels of toxins.

It is thought that the contaminated animals were washed up on beaches during winter storms and are likely to have now been washed back into the sea.

Eastern Inshore Fisheries and Conservation Authority (Eastern IFCA) is co-ordinating the activity of relevant agencies in seeking to establish the source and extent of the PSP contamination.

The CEO of Eastern IFCA Julian Gregory said: 'Any risk is only because of ingestion so our advice to the public remains the same.

'There is a low level of risk to beach users and their pets but as a precaution it is suggested that dogs are kept under close control, on leads or muzzled and people should avoid handling starfish. There is no risk to people or pets from seawater.'

Several dog owners reported their pets becoming sick or dying after ingesting washed up fish on the coastline in north Norfolk in early January.

Doug Thompson and Zelda Eady's labradors became seriously ill after eating fish on the beach near Holkham on January 1.

And Mike Hamilton's dog Bramble was sick after a walk at Cley on New Year's Eve.

Owners of pets that have become ill after consuming items on a beach should report the matter to the district or borough council for the area where the incident occurred.