The checks are being stolen and altered through a type of fraud called "check washing." It's a story we first brought you Thursday. More victims are now coming forward.
"It's one of the largest checks we write throughout the year," said Jen Wilkinson.
Jen Wilkinson at Vineyard 29 in St. Helena, didn't think twice when she mailed in the winery's property tax payment for $206,000. A short time later, she made a terrible discovery.
"It did not make it to the tax collector," said Jen Wilkinson.
PREVIOUS STORY: Dozens of property tax checks in Napa Co. were stolen through mail, officials say
The check was cashed, not by the Napa County Tax Collector, but by a business in St. Cloud, Florida. The vineyard's tax check was stolen and "washed" by fraudsters.
CORNELL BARNARD: "What was your reaction you saw it?"
"My stomach dropped. My heart started palpitating like crazy," Wilkinson said.
The vineyard is not alone.
"We had 60 lost checks in the last two days. Our normal amount during a two-day period this week would probably be six," said Napa County Treasurer and Tax Collector Robert Minahan.
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The stolen checks now total between $1 and $2 million, including one check from another Napa Valley vineyard for $225,000, which was washed and cashed in Florida.
After our story aired on Thursday, more possible victims reached out.
"We received three calls from individuals who saw the story, who had mailed in their checks, but we never got them," Minahen said.
Minahen believes this goes beyond fishing envelopes out of a mailbox. He says the checks are being intercepted somewhere between Oakland's U.S. Mail processing center and his office.
Postal inspectors are on the case.
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"This is a concern to postal inspectors in the Bay Area and across the country. Unfortunately, there's no limit to the means criminals will use to try and get other people's property out of the mail," said Matthew Norfleet, U.S. Postal Inspector.
"I called our bank right away," Wilkinson said.
Wilkinson caught the fraud right away and is optimistic about getting the vineyard's stolen money recovered.
But other taxpayers may not know they've been ripped off. Late payment reminders are now in the mail.
"About 3,400 delinquent letters will be getting to our taxpayers this week. I think there'll be some surprises," Minahen said.
The Taxpayers Office urges property owners to check their bank statements and to pay their property tax bill online. If you suspect you have been the victim of fraud, call the Napa County Tax Collector's Office at (707) 253-4312.