The number people infected with paratyphoid fever continues to rise, with 10 cases now confirmed by the Hawke's Bay District Health Board.
The first three hospitalisations for the typhoid-like illness were two weeks ago.
A number of cases, who have had paratyphoid confirmed, have required hospital care at Hawke's Bay Hospital, and another has needed treatment in Auckland.
Some cases had been linked to mussels gathered from Napier's Ahuriri area, including some consumed at a Tangi at Tangoio Marae around 11 September.
Now, the Hawke's Bay District Health Board has identified a link to another tangi recently held at Flaxmere's Te Aranga Marae between August 28 and 30.
Medical Officer of Health Dr Nick Jones said the district health board was liaising directly with each marae where the tangi were held.
He said people must heed the warning signs and not gather shellfish from the Napier Marina area.
"We have had some preliminary results back on mussels collected for sampling from the Napier Marina area on Saturday, September 23, which showed they were still contaminated.
"We are awaiting final results of the types of bugs, but all the mussels had E. coli which indicated they had been contaminated with faecal matter."
The district health board was also working with the Napier City Council and the Hawke's Bay Regional Council to investigate possible causes to the outbreak.
Paratyphoid generally occurs within 10 days of consuming contaminated food or water but symptoms may take as long as four weeks to develop.
People with paratyphoid will have a fever, chills, headache, possibly a rash and may also get severe vomiting and diarrhoea.
Dr Jones said the district health board had teams continuing to work in the community to follow up with anyone who was sick, but the most important thing was to get medical help for anyone who was thought to be sick.
-Anyone feeling sick and who has eaten shellfish from the Napier Marina area should contact their family doctor or they could call HealthLine 24/7 0800 611 116.
-More information on how to protect yourself and others is available from here: www.ourhealthhb.nz