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What: Another day, another big move for snack and nut kingpin Diamond Foods (Nasdaq: DMND). Today, shares slid as much as 11% on reports that the U.S. Department of Justice has joined the list of agencies investigating the company.

So what: The company was already under investigation for its accounting practices around payments to walnut growers. The revelation of the criminal investigation is just the latest chapter in the debacle, but it is once again raising concerns that the company's deal to buy Pringles from Procter & Gamble (NYSE: PG) may be in jeopardy. The deal was expected to be financed largely with Diamond stock and Reuters noted the suspicion that payments to walnut growers may have been delayed in order to make Diamond's earnings look better while negotiating the deal.

Now what: As 2011 closed out, Diamond shares got a bump from rumors that hedge fund magnate David Einhorn was buying. I've yet to see evidence that that rumor ended up proving true. And if Einhorn did buy, he didn't buy a substantial enough stake that it had to be reported immediately.

What we do know, as of yesterday, is that some major Diamond shareholders have dumped their stakes in the company. Both Del Mar Asset Management and Baron Capital filed paperwork showing that they'd sold substantially all of their shares in Diamond. As of Sept. 30, Del Mar owned 8.7% of the company and Baron had a 6.9% stake.

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Fool contributor Matt Koppenheffer does not have a financial interest in any of the companies mentioned. You can check out what Matt is keeping an eye on by visiting his CAPS portfolio, or you can follow Matt on Twitter @KoppTheFool or Facebook. The Fool's disclosure policy prefers dividends over a sharp stick in the eye.