North Yorkshire Council’s assistant chief executive for localities, Rachel Joyce, said: "Late last week and over the weekend a number of dead birds have washed up on Filey and Scarborough beaches.
"We understand there may also be similar instances elsewhere outside of North Yorkshire.
“The numbers have been reducing each day and we are working with Defra, which is the investigating agency, and other partners to determine the cause and take appropriate actions.
"If anyone spots any dead or sick birds they must not to touch them but should report them to Defra, providing as many details as possible.
"Visitors must also adhere to any cordons in place, and we strongly urge pet owners to keep dogs on leads at this time."
Members of the public are encouraged to report findings of dead wild birds in Great Britain using the online reporting system or by calling the Defra helpline if they find one or more dead wild bird of prey, swan, goose or duck, or five or more dead gulls or other dead wild birds of any species.
Reports to the Defra Helpline of found dead wild birds are triaged and not all birds will be collected.
An Animal and Plant Health Agency spokesperson said: “We are aware of a number of wild bird deaths along the North Yorkshire coast and seabirds from this area have recently tested positive for avian influenza H5N1 through our wild bird surveillance programme.
“We advise members of the public to not touch or pick up any dead or visible sick birds that they find.
"They should continue to report any findings through our online reporting system or by calling the Defra helpline on 03459 33 55 77.”
The Animal and Plant Health Agency (APHA) carries out year-round surveillance of dead wild birds submitted via public reports and warden patrols as part of its wild bird surveillance programme.
Wild birds are susceptible to a range of diseases and injuries and not all dead birds will have been infected with avian influenza.