Election officials in states across the country are continuing to scrutinize questionable voter registration forms submitted by an advocacy group that was raided Tuesday by Nevada authorities investigating voter fraud allegations. 

In Missouri, Jackson County's top election official, Charlene Davis, says they've discovered more than 800 potentially fraudulent forms from the Association of Community Organizations for Reform Now, or ACORN. 

She said they were bogging down work Wednesday, the final day Missourians could register to vote. 

"I don't even know the entire scope of it because registrations are coming in so heavy," Davis said. "We have identified about 100 duplicates, and probably 280 addresses that don't exist, people who have driver's license numbers that won't verify or Social Security numbers that won't verify. Some have no address at all."  

Officials said one name was registered 10 times, all with different birthdays and social security numbers, but with what appeared to be the same signature. Officials said ACORN employees even tried to register a 12-year-old. 

The nonpartisan group works to recruit low-income voters, who tend to lean Democratic. Polls show Republican presidential candidate John McCain with an edge in bellwether Missouri, but Democrat Barack Obama continues to put up a strong fight. 

Jess Ordower, Midwest director of ACORN, said his group hasn't done any registrations in Kansas City since late August. He said he was told three weeks ago by election officials that there were only about 135 questionable cards -- 85 of them duplicates. 

"They keep telling different people different things," he said. "They gave us a list of 130, then told someone else it was 1,000." 

FBI spokeswoman Bridget Patton said the agency has been in contact with elections officials about potential voter fraud and plans to investigate. 

"It's a matter we take very seriously," Patton said. "It is against the law to register someone to vote who does not fall within the parameters to vote, or to put someone on there falsely." 

In Ohio, the Cleveland Plain Dealer reported Wednesday that local ACORN representatives told members of the Cuyahoga County elections board that they could not eliminate voter fraud from their operation. 

On Tuesday, authorities in Nevada seized records from ACORN after finding fraudulent registration forms that included the starting lineup of the Dallas Cowboys. 

In April, eight ACORN workers in St. Louis city and county pleaded guilty to federal election fraud for submitting false registration cards for the 2006 election. U.S. Attorney Catherine Hanaway said they submitted cards with false addresses and names and forged signatures. 

Ordower said Wednesday that ACORN registered about 53,500 people in Missouri this year. He believes his group is being targeted because some politicians don't want that many low-income people having a voice. 

"It's par for the course," he said. "When you're doing more registrations than anyone else in the country, some don't want low-income people being empowered to vote. There are pretty targeted attacks on us, but we're proud to be out there doing the patriotic thing getting people registered to vote." 

Republicans are among ACORN's loudest critics. At a campaign stop in Bethlehem, Pa., supporters of John McCain interrupted his remarks Wednesday by shouting, "No more ACORN."  

There are at least 11 investigations across the country involving thousands of potentially fraudulent ACORN forms. 

According to its national Web site, the group has registered 1.3 million people nationwide for the Nov. 4 election. It also has encountered complaints of fraud stemming from registration efforts in Wisconsin, New Mexico, Nevada and battleground states like Michigan, Ohio and North Carolina, where new voter registrations have favored Democrats nearly 4 to 1 since the beginning of this year. 

Missouri offers 11 electoral votes; the presidential candidates need at least 270 to win the election. 

FOX News' Eric Shawn and The Associated Press contributed to this report.