Gore District Council will review security at its waste water treament plant after a boy drowned last night.
The three-year-old boy was found unresponsive in an oxidation pond in Gore shortly after 11pm.
He was unable to resuscitated.
The pond is one of two owned and operated by the council as part of its waste water treatment plant in south Gore.
Council chief executive Stephen Parry said the council would urgently review security and fencing at the ponds.
"The relevant authorities have been notified and we will work closely with them," Mr Parry said.
Gore District mayor Tracy Hicks said he offered his deepest sympathy to the family of the boy.
"This is an absolute tragedy and will be felt by many in our small, close knit community," Mr Hicks said.
The police were making inquiries on behalf of the Coroner.
The tragedy unfolded when Gore police were alerted to a missing boy at about 9.30pm last night.
When it was reported to police a search had already been started by family, friends and neighbours.