The Ministry for Primary Industries has referred evidence of potential serious staff misconduct to the Serious Fraud Office.
MPI had also referred the matter to the State Services Commission as part of the commission's inquiry into the use of external security consultants, including private investigation firm Thompson & Clark.
The conduct did not involve the contracting of Thompson & Clark by MPI but to other matters, said MPI director-general Martyn Dunne.
Information obtained so far suggested these matters occurred prior to October 2013 and involved staff no longer working for MPI," he said in a statement.
MPI was extremely disappointed by the nature of the potential misconduct.
Measures were underway internally to understand how the matters may have occurred, even though they occurred some years ago.
"This will contribute to a 'lessons learned' exercise to ensure they cannot happen in the future. We are confident that current processes, structure and culture make it unlikely these events would occur now," Dunne said.
MPI revealed last month it had uncovered the misconduct as part of the preparation of a response to an Official Information Act request for all correspondence between MPI employees and Thompson & Clark Investigations Ltd (TCIL).
"MPI entrusts its people with responsibilities that are bound by a number of legislative frameworks. Our behaviour as state sector employees is also guided by the SSC Code of Conduct and by the Privacy Act," acting director-general Bryan Wilson said last month.
"We are extremely disappointed to learn that past employees of this organisation potentially breached our code of conduct, our trust, and by proxy the trust that was given to them by the New Zealanders that we serve," he said in a statement.
State Services Commissioner Peter Hughes has widened an inquiry into the use of Thompson and Clark to cover all state sector agencies.
Hughes said last month he decided to expand the inquiry after information about other Government agencies surfaced.
Hughes said the fresh material that persuaded him to expand the inquiry came to light in Official Information Act requests to MPI and the New Zealand Security Intelligence Service.
"What I have seen raises serious questions about the nature of engagement between Thompson and Clark and state sector agencies," Hughes said in a statement.
Hughes appointed Doug Martin in March to investigate the use of Thompson and Clark and other security firms by Southern Response.
Martin is looking into whether the Southern Response agency, set up to settle quake insurance claims, spied on claimants.
That inquiry was expanded shortly afterwards to include the Ministry of Business, Innovation and Employment's (MBIE's) relationship with Thompson and Clark. Activist groups say they have been spied on by Thompson and Clark for MBIE.
Hughes has also appointed high-profile Auckland barrister Simon Mount QC to the investigation team.
Director-General of Security Rebecca Kitteridge has also launched an investigation into the conduct of some SIS staff after correspondence raised concern about favourable bias towards Thompson and Clark.