Thirty-one more North District Hospital staff have developed gastroenteritis symptoms after eating food provided by a caterer at a party, bringing the total number of affected people to 69.

The six men and 63 women aged 17 to 58 came down with abdominal pain, vomiting and diarrhoea after eating at the January 23 party.

Six sought treatment the hospital's accident and emergency department or from private doctors. None required hospitalisation.

The Centre for Health Protection has referred the case to the Food & Environmental Hygiene Department which is collecting samples for laboratory tests.