Updated

An Indiana prosecutor has opened an investigation into claims that hundreds of signatures were faked on petitions for Barack Obama and Hillary Clinton in the state's 2008 presidential primary, as the chairman of the St. Joseph County Democratic Party resigned amid the scandal.

Despite calls for a federal investigation, St. Joseph County Prosecuting Attorney Michael Dvorak said in a statement that the U.S. attorney for the region would not investigate claims regarding petition fraud. Dvorak instead has opened a probe of the allegations and issued a request that the Indiana State Police assist in the investigation.

The announcement comes after the local Democratic party chairman, Butch Morgan, announced his resignation in a statement Monday, saying, "After consulting with the Indiana Democratic State Party, I am stepping down as chairman of the St. Joseph County Democratic Party and as chairman of the Second District Democratic Party, effective today."

Morgan, who's been the county chairman since 1995, denied any wrongdoing and said he "regrets" having to resign.

"I hope no one will misinterpret the reasons for my resignation," Morgan said, "I have done nothing wrong and I look forward to an investigation that will exonerate me of any wrongdoing."

Indiana's Republican and Democratic Party chairmen had called for a federal investigation into the forged names that appeared on petitions from the 2nd Congressional District, which contains St. Joseph County. Among the dozens of names so far discovered to be fake are former Indiana Democratic Gov. Joe Kernan.

Kernan told the South Bend Tribune last week that neither the print version of his name nor the signature that appears on the suspect document is anything like his own.

Yet, his and other names were approved by the county voter registration office with the use of a rubber stamp in place of a signature by the Republican member of the office.

The Tribune reported that the St. Joseph County voter registration office has a Democratic and Republican member who sign off on petition pages submitted for review. However, Republican Linda Silcott was out of the office on bereavement leave on the days the suspected fakes passed through her office.

Silcott's stamped signature is used on the suspect pages while Democrat Pam Brunette signed off on the petitions in her own hand. The Tribune reported that Silcott's deputy, Mary Carrol Ringler, has authority to use the stamp, but she does not recall if she did so, in part because the dates of the forged petitions coincide with her first two weeks in her post.

On Friday Indiana Republican Party Chairman Eric Holcomb submitted a request for a federal probe to be conducted by the Department of Justice.

"What I want to know going forward is what happened, who was involved, and what the appropriate punishment is for that crime. We know that there are potentially, as we read, if the reports are true, that there were hundreds of crimes committed. And so, right now, today, this minute, we're only talking about one county in one state but this may be, in fact, the tip of the iceberg. And I'm sure to learn more as the facts come into the light," he said in a news conference.

Indiana Democratic Party Chairman Dan Parker told the Evansville Courier & Press last week that he supports an investigation.

"Even an isolated instance of misconduct, by one individual among the hundreds of volunteers working to collect signatures for the candidates, should be thoroughly investigated, and we support such an inquiry," he reportedly said last week.

Morgan's attorney Shaw R. Friedman said the chairman decided to resign after conferring with state party officials "that remaining on in any capacity would be an unwanted distraction for candidates in the upcoming city elections." Friedman noted that Morgan has "did not personally authorize, direct or condone the forgery or alteration of petition signatures."

To get on Indiana's ballot, statewide candidates must get at least 4,500 signatures -- 500 each from the state's nine congressional districts.