ATLANTA -- Federal officials have asked election officials in Georgia and five other states to investigate whether citizenship checks are being improperly run on newly registered voters.

Social Security Commissioner Michael Astrue sent a letter Friday to the secretaries of state of Alabama, Georgia, Indiana, Nevada, North Carolina and Ohio. Astrue said those states had submitted "extraordinarily high levels" of citizenship verification requests.

Under the Help America Vote Act of 2002, most states only have to verify the last four digits of the Social Security Number of people seeking to register to vote if they don't have a valid state driver's license.