Potential IRS lien on a property won "free & clear"

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Hello - I recently won a property at a Pennsylvania Sheriff's Sale auction. It was auctioned with a "free and clear" title. There are currently tenants residing there who referred me to their landlord (property owner not residing at the location). Interestingly, the property owner was rather polite in our initial phone discussion and his major concern was for me! The property owner said to "be careful" because he has had issues with the IRS and as a result there is an IRS lien on the property. Further, that the county, which sold the property "free and clear" of any liens, does not have the authority to clear IRS/Federal liens. My question is, is this possible? Or is the current owner just trying to scare me away? Can a lien still exist on the property even if the county lawyers advertised and sold it as "free and clear?" I'm not sure what my next steps are so any insight would be greatly appreciated! Thank you!