The Civil Rights Division of the U.S. Justice Department has opened an investigation of Pennsylvania's new voter ID law, asking the Corbett administration to document its repeated claims that 99 percent of the state's voters have the photo identification they will need to vote in November.

In a letter delivered Monday to Secretary of the Commonwealth Carol Aichele, the Justice Department sought a series of databases and other records that have raised questions about the number of registered voters with proper ID, and left county election boards and the public bewildered about the impact of the new voting requirements.

The Justice Department said it needed the information "so that we may properly evaluate Pennsylvania's compliance with Section 2 of the Voting Rights Act and other federal voting-rights laws."

That section of federal law prohibits laws or practices that discriminate against any citizen because of race, color, or language.

An unrelated lawsuit by the American Civil Liberties Union and other groups, challenging the new voting requirements as a violation of the state constitution, is scheduled for hearings Wednesday in Harrisburg before Commonwealth Court Judge Robert Simpson.

His decision, expected by mid-August, may be appealed to the state Supreme Court, now divided 3-3 between justices elected as Republicans and Democrats.

The items requested by the federal government include the state's complete voter-registration list - identifying the state's 8.2 million voters by their names and addresses, dates of birth, party affiliations, and voting histories - and the state Transportation Department's full list of people holding driver's licenses and nondriver photo IDs, the most common form of photo identification that will meet the demands of the state's new voting law.

It was the reported mismatch between those two databases - Aichele's July 3 statement that up to 758,000 voters statewide, about 9.2 percent of the electorate, did not have PennDot identification - that has refueled concern over whether the new law would disenfranchise thousands of legitimate voters.

Another data set, distributed last week to county election boards without any public announcement, disclosed that thousands of additional voters could lose their voting rights because their PennDot ID expired last year or earlier.

In Philadelphia, the state counted up to 186,830 voters without PennDot ID, 18 percent of the city's registered voters. But the Department of State cautioned that about 50,000 of the total were inactive, not having voted in at least four years, and that others were listed as mismatches because the same people used different first names between their voting and PennDot records.

Last week, the state announced it would create a new ID card, available in late August, for would-be voters who provide their date of birth and a Social Security number, along with documentation of where they live, such as utility bills. Further details are not yet available.

Besides asking for state data on Pennsylvania voters and drivers, Assistant U.S. Attorney General Thomas E. Perez, the head of the civil-rights division, asked the state to produce "any documents or records supporting the statement in the governor of Pennsylvania's press release dated March 14, 2012" - announcing Corbett's approval of the voter ID bill - "that 99 percent of Pennsylvania's eligible voters already have acceptable photo IDs.'"

Also requested from the state were documents reflecting its implantation plans.

A spokeswoman for Corbett's office, Janet Kelley, confirmed the receipt of the Justice Department's letter and said the state would gather the information requested.

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