Following questions raised by the ministry's management team, an internal investigation found that suspicious payments had been made to various entities and the matter was referred to the SFO.
The office allege the Ministry of Transport paid approximately $726,000 to entities associated with Ms Harrison.
During her time with the ministry, Harrison's role included responsibility for change, people and development; communication and external relations; administration and ministerial support; knowledge management and information and the shared services programme management, the SFO said in a statement.