We had mice in our townhouse, which we noticed shortly after we first moved in. Our landlord shrugged and gave us some poison cubes to put around. That did nothing as they were running around in the basement ceiling.
Instead we took matters into our own hands, we tore out the drop ceiling in the basement where they were nesting, cleaned up the huge amount of mouse droppings and carcasses that fell and put up mesh by our dryer vent which was where they were entering from. Most of the drop ceiling tiles were stained on the other side form mouse urine.
Our landlord was surprised we did this, thankfully he didn't care that we tore out the ceiling since he's not the owner of the property.
OP, better get on this before your tenants try to take matters into their own hands, it'd be a shame if they make a few holes in walls and ceilings in an attempt to get rid of the mice in YOUR property.