[cnn-photo-caption image= http://i2.cdn.turner.com/cnn/2008/images/10/16/art.macpt1016.gi.jpg caption="At the final presidential debate, Sen. McCain said ACORN might be destroying the fabric of democracy."]
(CNN) – In the wake of an Associated Press report that the FBI is reviewing the results of several state inquiries into the conduct of ACORN, Sen. John McCain’s campaign called Thursday for Sen. Barack Obama to release additional information about the relationship between the embattled community organizing group and the Obama campaign.
“Barack Obama’s campaign must fully disclose the nature of his association with ACORN,” McCain campaign manager Rick Davis said in a statement Thursday.
The Obama campaign took issue with the McCain campaign's request. "ACORN never performed any voter registration work for the Obama campaign and Senator McCain’s campaign knows this," the Obama campaign said in an e-mail to CNN. "The real question is why they continue to assert something that isn’t true, and why they believe that attacking a group that Senator McCain himself praised as 'what makes America special' helps their campaign."
CNN has been unable to confirm a report by the Associated Press that the FBI is investigating whether ACORN helped foster voter registration fraud across the country as the presidential election approaches. Instead, several government sources have told CNN that the FBI and the Justice Department are reviewing documents provided by state investigations into ACORN to determine whether there is a basis to open a federal criminal investigation.
These developments at the federal level come nearly a week after six Republicans in the House of Representatives sent a letter to Attorney General Michael Mukasey requesting a federal investigation into ACORN’s voter registration activities. All of the House members who signed the letter to Mukasey had previously administered elections as Secretaries of States.
In a statement Thursday, ACORN said that it has not been contacted by any federal law enforcement agencies. "Should any investigation be forthcoming, we are confident that we would be exonerated," the group said. "We have always, and will continue to, work with any inquiry."
Watch: ACORN counters fraud charges
At the final presidential debate, Sen. McCain challenged Sen. Obama to explain his relationship with ACORN, saying the group “is now on the verge of maybe perpetrating one of the greatest frauds in voter history in this country, maybe destroying the fabric of democracy." In response, Obama said his only involvement with the group was representing it in a lawsuit against the State of Illinois regarding a motor voter law. A CNN Fact Check found Obama's claim to be false.
Earlier this week, Obama and senior officials from his campaign both said that the Obama campaign has its own voter registration efforts that are not related to ACORN’s recently completed voter registration drive.
Since the registration drive was recently completed, there have been several press reports of questionable or fraudulent voter registration forms submitted as a result of the drive.
Updated 8:55 pm to add comment from the Obama campaign.
–CNN Justice Department Producer Terry Frieden contributed to this report