Management Consultant and freelance adviser to a startup. Experienced in wide range of business-related areas such as Strategy, Program Development, Budgeting, Project Management and Mentoring.
No one can eliminate the possibility of theft in a business, but one can definitely minimize it. It all boils down to your front-liners and the level of integrity they have.
In this case, the workable solution is to look at your recruitment cycle. How is your current recruitment cycle looking like? Do you put in place any controls such as background checks on new hires, situation and behavioral interviews, etc? I find that if you can hire the right people, chances of fraud or theft is minimal, if not, completely zero.
It would also be worthwhile to re-look into your remuneration package as often, staff may steal due to low salary and high financial pressure.
Lastly, do look into the culture you are trying to institutionalize. If it is one of fear and "management by stick", do consider changing it, to something more empowering.