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John Stamos says he was targeted by a pair of alleged blackmailers who threatened to sell so-called compromising photos of him unless he coughed up $680,000.

Allison Coss, 23, and Scott Sippola, 30, of Marquette, Mich., were arrested last week in an FBI sting operation after they met with an undercover agent, posing as a Stamos representative, to collect their money in a Michigan airport, according to a Dec. 3 FBI affidavit obtained by

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After police raided their home, they discovered three photos of Stamos, a piece of paper with the actor's personal cell phone number on it, and a list of three tabloid magazines with contact numbers for each, according to the affidavit.

Stamos, described as "Mr. X" in affidavit, was vacationing in Florida in 2004 when he met Coss. At the time, the pair and another pal attended a party where photos were allegedly taken of the former Full House star, 46.

Following the party, the actor stayed in touch via email with Coss, according to the FBI.

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Last month, Stamos, now starring in the Broadway revival "Bye Bye Birdie," began receiving email threats from a person named "Brian L" who allegedly demanded $680,000 from Stamos or else the photos would be sold to a tabloid. In emails, Coss alerted Stamos that she was involved in the plot.

The affidavit did not describe the photos, but Stamos was told they would "cause harm" to his reputation if released. (No word whether the photos were taken before or after he and actress Rebecca Romijn announced their split that year).

Upon receiving the threats, Stamos called his attorney, who notified the FBI late last month, according to the affidavit.

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A rep for Stamos is insisting the photos in question are not risque, and are merely shots of him posing with fans. The photos also will likely be released to prove they are not damaging.

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