Mostly a good scrubbing. 

Oil base Kilz, Scrub everything down with TSP first and cover everything with the Kilz including the  concrete.

@Cristian Samayoa From what I've looked into, you can get a list from the Register of Wills and pay per entry, But then you have to scrub that list to see who has real property in their estate.

The problem I am having is no residential contractor is guaranteeing they can fix the issue then contractors flake etc.The tenants still want to be in the house which I find odd as I later found out water came into the garage and there is a lot of mold damage and I had another water restoration contractor removing the drywall and scrubbing the wood frame of the walls. 

I used a TSP solution to scrub the walls and cabinets in the kitchen.

I know list source pulls from public records and I am sure they have a huge stuff scrubbing and matching criteria but how and where do they get the raw data from?

It needed replacing because the tenant had scrubbed through the enamel and dented the sheet metal attempting to “clean” it.  

They like the brokers to do the grunt work of scrubbing sites and then if it looks possible then calling them to discuss.

Scrubbed with TSP, coat of Kilz and some paint...no more smell.

Supposedly it's best to send a postcard first because it's the cheapest and you'll get the non deliverables back returned to you so that you can further scrub your list or skip trace those returned cards and find the real addresses of the owners.