However, officers suspected the woman, seen on CCTV footage coming into a restaurant, is a local wanted on previous charges for dishonesty offending.
Police have been in contact with health authorities and checked in with the Public Health Office, which advised there had been no increase in food poisoning reports in the area made by a female.
Manukau said police had also been advised that it would be highly unlikely for a GP to have written the name of a restaurant on a medical certificate without "proper process having been followed".
"Based on the information we have gathered, we don't believe this woman has had food poisoning and we are advising any other retailers who have experienced a similar scenario to contact your local police station to report it."
Although Manukau said police believed they knew who the woman was, they'd still like to hear from anyone else who'd had an encounter with her.
She said small business owners may now be fearful that they've given someone food poisoning and put their business at risk.
"We don't believe they have, but instead they are possibly being scammed into paying money for fear of being accused of making a person sick."
While Manukau said it wasn't unheard of for someone who had been sick to contact a restaurant regarding food poisoning concerns, she said to show a medical certificate and ask for money was less common.
She urged anyone who'd had such an experience to contact police.
