A top former official at the Ministry of Transport is being investigated for serious fraud.
Joanne Harrison, who was the organisational development general manager, was stood down in April when the alleged fraud came to light, and is no longer an employee.
The ministry's chief executive, Peter Mersi, said she was a senior staff member in a position of high trust, and staff felt betrayed.
He said a number of reviews into the ministry's systems were under way and his focus was on ensuring that any misappropriated money was recovered.
"In light of what has happened, it is prudent to confirm that our systems, processes and controls are robust," he said.
"These focus on internal controls and recruitment processes."
The Serious Fraud Office (SFO) was also investigating, and Mr Mersi said he could not give any more details because of that investigation.
The SFO confirmed it had started an investigation.