FREEHOLD, N.J. — Worried that a design snafu on envelopes for mail-in ballots could create an anxious electorate, a county clerk set up a hot line so residents could determine whether their votes made it back to the Board of Elections.

The problem occurred because of the prominent display of a voter's return address on the front of the vote-by-mail ballots for Monmouth County and a few other New Jersey counties. The return address also has a bar code that the Board of Elections uses to process the votes.

But the large type near the destination address caused problems with postal machines' ability to read the destination, said Ray Daiutolo, U.S. Postal Service spokesman for southern New Jersey. And until postal officials learned of the problem last week, many early voters' ballots had been returned to sender.

Some people already expressed concern that voters who sent in their votes and left town might discover the ballots back in their mailboxes too late to be counted.

The return-address bar codes don't record a vote but do tell election officials whether a ballot they mailed out has come in, said Monmough County Clerk Christine Giordano Hanlon, whose office oversees mailing and preparation of the ballots that are sent to the County Board of Election. So when Monmouth County voters who sent a mail-in ballot call the hot line during county business hours, they can find out whether their ballot was received.

Last week the postal service alerted its staff to envelope problem and has been setting the mail-in ballots aside to be sent to the election board rather than returning them to the sender, Daiutolo said. Voters who receive ballots they already had mailed can mail them again without additional postage.

Follow Susanne Cervenka on Twitter: @scervenka