TAMPA, Fla. (AP) - The FBI is joining an investigation into bogus letters sent to many Florida voters that raise questions about their eligibility to cast ballots.
    
Tampa FBI chief Steven E. Ibison said Wednesday the FBI will focus on letters received by voters in 18 counties in central and southwest Florida. State authorities have received reports of letters in at least 23 counties.
    
The letters claim to be from county supervisors of elections but were all postmarked from Seattle. They raise questions about the voter's citizenship and appear intended to intimidate people.
    
Ibison says voters who get a letter should first contact their local election supervisor to see if it's authentic. If not, voters should keep the letter and contact the FBI.
    
The Florida Department of Law Enforcement has also opened an investigation.

(Copyright 2012 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.)