Mysterious Squatter/distressed property, A+ n'hood, what to do?

[Justin Hennig]

Have a distressed property I want to pursue that needs a ton of work but has awesome potential as a fix/refi/hold. The owner of record has deceased for a few years and the neighbor says the deceased owner's girlfriend still lives there. What steps can be taken to track down the estate and "relocate the quatter" to make a sale possible? Thanks for any assistance!