Fish & Game southern gamebird manager David Klee said the symptoms exhibited by birds in the area were consistent with the disease.
He said it was impossible to accurately establish how many birds have died because the site was subject to large tidal movements which may have washed dead or dying birds out into the Firth of Thames, beyond the range of Fish & Game's monitoring.
"We have received reports of birds washing up along the Thames coast and fishermen have reported seeing carcasses out at sea."
An operation, also involving the Department of Conservation, would be carried out tomorrow to try to halt the spread of the disease.
"It is possible to manage outbreaks of avian botulism by removing dead and dying birds and disposing of them in an appropriate manner," Mr Klee said.
"However, collecting a large number of carcasses over a wide area requires a lot of manpower. That's why we've rallied our game bird hunting licence holders and are calling on other volunteers to help out."
Anyone interested in helping can contact Mr Klee on (07) 849 1666 or 021 300 183 (after hours) or email dklee@awfg.org.nz.