If you have some doubts in the human decency of your housekeeping staff but you don’t have any real grounds for it, you can use two ways to settle this problem.
If you don’t want to cause offence to your employee with the groundless suspicions, you have to provide installation of the CCTV monitoring.
Review of the video recorder materials will help you to prove or to disprove your doubts. This way is more time-consuming.
If you are in a forceful mood you can use the polygraph (lie detector) test. In this case you will receive the answer at once.