ATLANTA --- The U.S. Department of Justice is questioning 2 million requests it says were made by Georgia officials since last fall to check the Social Security numbers of newly registered voters, far more than any other state.

In a letter sent to Georgia Attorney General Thurbert Baker, Justice Department officials said those checks appear to represent a substantial change in state law. They need federal clearance under the Voting Rights Act to ensure they "will not have the effect of discriminating on account of race, color, or membership in a language minority group," the letter said.

Justice Department Voting Section Chief Christopher Coates said that without preclearance, any voting changes are "legally unenforceable."

Matt Carrothers, a spokesman for Georgia Secretary of State Karen Handel, said she is consulting with the attorney general's office on how to proceed.

Mr. Carrothers said officials are trying to determine how the Social Security Administration arrived at the 2 million figure. That's far more than the number of new voters who registered in Georgia during the same period, he said. About 406,000 new voters have registered in 2008.

Under the Voting Rights Act of 1965, states with a history of discouraging minorities from casting ballots must get the Justice Department's approval for any voting changes.

Under the Help America Vote Act, states must verify information from new voters using a driver's license or Social Security database. Based on the checks elections officials have initiated, some counties have sent letters to residents asking them to provide proof they they're eligible to vote.

Alabama, Indiana, Nevada, North Carolina and Ohio also received letters.