There are several measures you can take to help prevent someone from stealing items in your office.

Lock all doors when you leave the office.

Instruct all employees to keep all valuables in locked desks when unattended.

Keep expensive items off desktops when unattended.

Do not leave articles of value - including handbags and coats in unguarded reception areas or on desks in offices, even for a few minutes.

Thoroughly mix your vault or safe combination when closing. Do not leave your vault or safe combination in a desk.

Notify Security or Management when loiterers are observed in corridors or washrooms. 

Peddlers and canvassers should be reported to the management office.