Can we search employees’ work areas while investigating a string of thefts?

Q. I work for an Internet company with about 50 other employees. Recently, there have been several complaints around the office about theft of personal property. The problem has become a distraction in the workplace and I was asked to investigate the incidents.

Our employee manual does not have any policies prohibiting theft of personal property, and there are no notices that warn employees that their work areas may be searched. What right does my company have to search a suspected employee’s work space and personal items to try to locate property not owned or related to my company? ...