INDIANAPOLIS | Secretary of State Connie Lawson has identified 727,000 potentially inaccurate voter registration records across Indiana.

A massive May postcard mailing to all 4.4 million registered Hoosier voters saw about 16 percent returned as undeliverable. Starting this week, the state is sending a second, forwardable postcard to those registrants urging them to update their address and voter registration data.

"Inaccurate voter information impairs the integrity of our voting process, and it artificially lowers our voter turnout statistics," Lawson said.

Hoosiers who receive a second postcard must update or confirm their voter information by July 24. Those who do not will be placed on "inactive" status.

Inactive registrants still can vote this year, in the 2015 municipal elections and 2016 elections. But inactive voters who fail cast a ballot or update their registrations by 2017 will become eligible for removal from the poll lists.

Voters who only received the first postcard, reminding them of the Nov. 4 general election, do not have to do anything.

All Hoosiers can confirm their voter registration online at indianavoters.in.gov.

Lawson, a Republican, doesn't suspect the high number of potentially inaccurate registrations is due to widespread voter registration fraud.

Instead, the former county clerk said people die or relocate to another state, and county voter registration offices often aren't notified.

Indiana's dismal 13 percent voter turnout in the May 6 primary election likely is due in part to the potentially high number of outdated voter registration records.

That was the lowest primary turnout in state history and 7 percentage points less than the previous record.

"Every election ... we get calls from widowed spouses and parents whose child moved away from home years ago, and these voters want to know why their loved ones' names are still on the rolls," Lawson said. "They not only find it upsetting to have a long-gone loved ones' name on the poll book, but it also undermines their faith in our election process."

Federal law requires states to regularly update their voter registration records and dictates the multiyear process for classifying inactive voters, contacting them and eventually purging them.

The Indiana General Assembly last year appropriated $2.1 million for the voter registration mailings.

Lawson, who was appointed secretary of state in 2012, said Indiana last conducted a thorough statewide voter registration records update in 2006, though many counties updated their lists since then.

However, not all counties have kept up, and in some, the number of registered voters now is higher than the number of adults living the county, Lawson said.

"Since becoming Indiana's chief elections officer, my goal has been to have an ongoing, comprehensive statewide program to get Indiana's voter lists regularly updated," Lawson said. "From now on, Indiana will do a regular voter list mailing in every even-numbered year."

The bipartisan co-directors of the secretary of state's election division are overseeing the current effort.

Improving voter turnout and participation is the top goal of Democrat Beth White, the Marion County clerk running against Lawson for secretary of state.

White claims Lawson, a former state senator, has used her offices to enact and enforce strict voter identification requirements and limit early-voting opportunities to discourage younger and new Hoosiers from participating in elections.