FBI investigates voter fraud in key states

>>> 11 days, but the fbi is investigating alleged vote are fraud and intimidation in key states. meantime watchdog groups are worried about what they call a surge of quote dirty tricks . nbc news national investigative correspondent michael isikoff has details.

>> reporter: the official looking letters are showing up across florida , challenging voters citizenship and theirose getting th em are outraged.

>> i went ballistic when i read it.

>> they questioned my citizenship and were implying they were going to eliminate me from being able to vote.

>> reporter: the fake letters which threaten nonregistered florida voters with arrests and imprisonment were post marked in seattle. the fbi is trying to track down the perpetrators. florida officials are alarmed.

>> this is an attempt to intimidate voters in one of the most important states in the united states in a national election.

>> reporter: members of both parties and independents have received the phoney letters although a majority have seem to have gone to republicans even 2001 the state gop chairman. watchdog groups say it's one of many dirty tricks popping up aimed at voter suppression .

>> we've seen earlier in the election cycle than previous years these underhanded tactics by shadowy groups to restrict the ability of responsible americans to vote.

>> reporter: the dirty tricks include billboards in minority neighborhoods warning that vote fraud is a felony. put up by an unnamed private family foundation they are now coming down after a public outcry. in arizona some hispanic voters received official notice , listing the election as november 8th , two days after election day . just this week a conservative activist group caught the son of virginia democratic congressman jim moran in an undercover video sting seeming to go along with a plan to cast fraudulent ballots.

>> utility bills, so you have that.

>> his son said he was trying to humor the person that approached him but quit the campaign and local police are investigating. meanwhile virginia attorney general ken cuccinelli is investigating a republican operative arrested for throwing voter registration forms in a dumpster. operative colin small who couldn't be reached for comment had previously work for strategic allied consulting, a consulting firm fired by the republican national committee last month after employees turned in hundreds of suspicious registration forms in florida , including some with fake addresses like a shell gas station . at the time the head of the firm told nbc news he was the victim of a few bad apples that work for him.