Dozens of Napa County homeowners now have some answers as to why their property tax payments had not made it to the county tax collector this spring, and/or why the checks were getting deposited in other states.

The first piece of the puzzle has arrived in a mysterious case involving property tax checks that were disappearing in Napa County. Authorities say that nearly 50 Napa homeowners who used paper checks and the US mail to pay their property taxes had those checks stolen out of the mail, "washed," and desposited into accounts in multiple states.

ABC 7 first reported on the checks disappearing last month, when Napa County Treasurer and Tax Collector Robert Minahen put out an alert that around $1.5 million had been stolen in this fraud scheme.

In one case, a Napa vineyard owner cut a sizeable check for $225,000 which later had its payee information altered to a Florida LLC, and deposted there.

The FBI got involved, and they just announced an arrest that was made back in April in Phoenix, where at least a few of the checks had been deposited into one man's account there.

That suspect has been identified as Ricco Jackson, and as ABC 7 reports, he was arrested after he showed up at his bank to ask why his account had been frozen. Jackson allegedly deposited five checks into the account of a fake LLC in Phoenix, totaling $103,000. Jackson will now head to trial in federal court in August.

The investigation is continuing, and more arrests are likely to follow. The FBI believes that this is partly an inside job involving someone working for the US Postal Service who is intercepting mail in a targeted fashion.

As Minahan tells ABC 7, "I think you have somebody locally who's doing the stealing, somebody within the Bay Area between the Oakland post office, postal facility processing, and our office. And, they're then disseminating these stolen checks throughout the country."

In addition to Phoenix, stolen and washed checks have been deposited so far in Georgia, Florida, and North Carolina.

Minahan said that all but one bank had issued reimbursements to customers, and those have totaled $1.4 million to date. And he's encouraging everyone to pay their property taxes online instead of by mail.

A similar scheme, which appears to have remained unsolved, was happening last year in Santa Clara County. ABC 7's 7 On Your Side spoke to one San Jose property owner, Paul Glaser, whose $28,000 property tax check was stolen and cashed late last year, and as of February, his bank, Wells Fargo, was refusing to reimburse him.