Stephen Savage, director of regulatory services and public protection, said: "The event organisers are cooperating fully and we are continuing to investigate the source of the outbreak.
"Please can anyone with symptoms contact Regulatory Services and Public Protection at the City Council on 0191 278 7878."
Dr Kirsty Foster, of the Health Protection Agency and chair of the outbreak control team, said: "Initial investigations have not yet identified a definite source of infection however we are working closely with the organisers of the event to determine the source of infection.
"Anyone who is concerned about symptoms suggesting salmonella infection should contact their GP or out of hours service in the first instance.
"Those affected should not return to their place of work until their symptoms have ceased for 48 hours."