The tenant can call the police, and they will order you to let them back in.This is really really basic info, essentially Landlording 101.  

If you can't find them, call the police and ask who they use.  

I was fortunate to live in a city where the police actually showed up and quickly.  

You at 8:53, Aug 17:Since they are moved and I can not contact them can I go in and change the locks to secure the propertyChijioke at 8:54, Aug 17:yesYou at 8:54, Aug 17:What about anything left behindYou at 8:55, Aug 17:Can I call and have a police officer walk in with meChijioke at 8:55, Aug 17:you can, I am not sure if they willYou at 8:56, Aug 17:What about items they have left behind ?

My lawyer subpoenaed a police officer from the drugs squad to testify and we had quite the Law and Order episode.

And thought I was getting somewhere, but the wife came home she called the police. 

The neighbors called me and I arrived just before the police did.

Then, there were the neighbors that can't stand the endless traffic and start calling the Police.

What's usually required is that Proof of executor for the tenants estate is obtained before you permit anyone other than police to remove anything from apartment.. the person that contacted you should provide authorization from a  attorney or give you name of executor, so you can release the unit to them.

Your city may require you to attend a Crime Free/Drug Free class to be certified, this is a good class and get set up and take it, call your police department where the property is located and find out more.Apartment buildings are sold everyday, Some with 100's of current tenants with leases that are transferred so your not assuming something that other landlords haven't done and will continue to do.