WASHINGTON - Twin Cities prosecutors are investigating hundreds of cases of suspected voter fraud flagged by Minnesota Majority, a conservative group that claims large numbers of ineligible felons were allowed to vote in the 2008 elections.

Initial reviews by state and local officials, however, indicate that the problem may be far smaller than the group found in a recent study being championed by the Minnesota Republican Party.

The Ramsey County Attorney's Office said Monday it is investigating about 180 cases out of 500 that were brought forward by Minnesota Majority, which recently completed an 18-month study of state voter and criminal conviction lists. Charges were brought against 28 felons for allegedly voting or registering illegally in 2008. But another 267 reports were found to be "inaccurate" after an initial review, according to Ramsey County Prosecution Division Director Phil Carruthers.

Deputy Hennepin County Attorney Pat Diamond said his office is still looking at 216 allegations flagged by Minnesota Majority, out of 451 that were brought forward by the group. No charges have been brought as a result of the report, though a handful of other individuals have been charged with fraudulent voting.

Both prosecutors said they are using several extra investigators to look at the rest of the reports.

According to a report released two weeks ago by Minnesota Majority, 1,359 names of suspected ineligible felons were forwarded to these two counties for investigation.

But local and state officials say the group's reports are likely inflated and hard to verify because of difficulties determining whether the suspected felon voters had their voting rights restored, if they knew they were ineligible to vote, or if they were actually the people whose names appear on voter rolls.

"Illegal, to my mind, means prosecutable," Diamond said.

"Overwhelmingly, their statistics were not accurate," Carruthers said. "But I would say they did the best they could, given their access to the databases."

The Minnesota Republican Party seized on the Minnesota Majority report Monday to raise questions about the validity of the 2008 Senate race, in which DFLer Al Franken edged out Republican incumbent Norm Coleman by 312 votes after a long court battle.

But Minnesota Majority Executive Director Dan McGrath said that while there's a "possibility" that illegal voting by felons could have made the difference, there's no way to know, since ballots are secret.

"That's not the point we're trying to make," McGrath said. "The point is there's a problem and we want to prevent its recurrence."

Kevin Diaz is a correspondent in the Star Tribune Washington Bureau.