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Since when does a law firm need a bank to save it from falling for a Nigerian scam?

That's the case in Minnesota, where a firm of legal eagles that got tricked out of nearly $400,000 in a scam that has cost more than 80 law firms and attorneys some $31 million is suing Wells Fargo for not noticing a bogus check.

The con is believed to have started in the African nation that has given birth to a host of similar schemes. The Minnesota firm was stung by a con artist posing as a 40-year-old Korean woman injured in an accident while in Minnesota, who claimed she was owed money from a settlement. Authorities believe she was part of a ring headed by Emmanuel Ekhator, who Nigeria recently agreed to extradite to the U.S.

Here's how it worked: A phony client contacts a law firm asking for help collecting a debt. The firm demands payment from the debtor - who is really a cohort of the scammer. When the cohort sends in a phony check, the law firm deposits it and deducts its fees. It sends along the balance to the bogus client, who is long gone by the time the bank - and the firm - discover the check is phony.

More than 200 lawyers or firms caught on before getting burned, but Milavetz, Gallop & Milavetz, of Edina, Minn., was one of dozens to get scorched. But this firm did what law firms do best: It sued.

In a 50-page lawsuit filed last week in U.S. District Court in St. Louis, the firm claims Wells Fargo had ample warning that a Nigerian-based fraud ring was targeting U.S. attorneys in 2009 and should have noticed "numerous inaccuracies" on the check. But, says the firm, the bank ignored red flags and allowed the phony client's share of the collected debt to be wired to a bank in Hong Kong, where it disappeared.

"Wells Fargo did not issue the wire transfer in good faith because it failed to notice numerous red flags surrounding the circumstances of the transaction and the appearance of the check," the lawsuit reads.

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The "most obvious" flag was that the branch's address written on the check was misspelled, according to the suit.

Robert Milavetz told FoxNews.com the lawsuit, which seeks to have a judge reverse the $396,500 charge to the law firm's trust account, will prevail in court.

"We're going to make sure they follow the law when it comes to handling accounts," Milavetz said on Wednesday. "A bank should be honest with its customers."

In a statement to FoxNews.com, representatives at Wells Fargo denied the allegations.

"We believe the allegations have no merit," the statement read. "We will vigorously defend, and expect to prevail."