How can you find out where the problem lies and determine how to resolve it?

Topic: Team Building

You are the GM of a large hotel where lately many housekeeping supplies have gone missing. The assistant to the security director initially approached the housekeeping director saying, “We know someone in your department has been pilfering from the storeroom or housekeeping carts, and I am here to find out who it is.” Now the housekeeping staff do not want to speak to the security department.

How can you resolve the communication issue and make them more of a team?