tenant that left did not give the keys

[Sami Gren]

HI,

I have a tenant that on last renewal notice they signed that they won't be renewing the lease, in fact they already moved but still have some stuff to take out, I did give them the extra few days, now I was going to pick up the keys as they were supposed to finish up taking out everything, 

and they just told me that they had an emergency and could not come today.

can I legally call my locksmith to open the lock and change it while they still have their stuff?

I just want to make sure that by law it is totally fine, if they cannot claim that they still live there and the only way to lock out would be through court

thank you