It depends on which state your property locates.

Better to get a police report, post a notice of abandonment (give certain time frame for the tenants to respond to your notice and pick up their property) on the inside of the main entry and take a picture. If tenants did not respond to your notice within this time frame, you may re-key and put their stuff in a storage for certain period of time (may or may not apply depend on where you are). 

Best result is if you can get contact with your tenants and let them sign a notice of tenants intent to vacate, then you can do what ever you want. Hope this will help, consult with a local (property location) real estate lawyer first.