For more than 20 years, Bryce Werling has been able to understand any damage to his roadside mailbox as the work of teen-age vandals and the harsh wind that whips across central Iowa.

But the destruction Friday, when a pipe bomb planted inside the rural mailbox exploded, injuring his wife Delores, defies logic, the 73-year-old retired farmer said.

"There is no way you could have told me this was going to happen to us," said Werling, whose farm is one of dozens fanning out across rolling landscape for miles in every direction.

Delores Werling, 70, suffered minor injuries to her arm and face, but has yet to fully regain her hearing, her husband said. Doctors say there's a 50-50 chance her hearing will return, Bryce Werling said.

The Werlings' mailbox was one of eight in a roughly 120-mile radius in Iowa and Illinois in which pipe bombs were found Friday.

Four postal workers and two residents were injured when they trigged the explosives by opening the mailboxes doors. Two other devices did not detonate, authorities said. None of the injuries was life threatening.

Ken Reinhart, a retired Chicago teacher who moved to Morrison, Ill., four years ago, said the bomb that exploded in a mailbox just outside town on Friday has made residents forget their provincial worries over noisy freight trains.

"That was the number one thing in the newspaper, was the train whistle," he said. "It's a big contrast now. The way things have gone since Sept. 11, it looks like this is how we're going to have to lead our lives."

Mail delivery in affected rural areas was suspended Saturday, and postal officials said they do not yet know when deliveries will resume.

In the isolated farm communities, collecting the day's mail is a welcome ritual and social connection for those whose closest neighbor is often a quarter-mile or more away.

Neighbors of the Werlings said they were stunned that violence targeting innocent people had happen so close to home.

Lucille Schemehorn, 87, said she couldn't figure out why someone would want to blow up the mail box outside her home near Elizabeth, Ill.

"I mean if it were for revenge that's one thing. But I ain't got an enemy in the world that I know of," she said.

Along the rural routes outside Morrison, Ill., where mail carrier Marilyn Dolieslager was injured in an explosion Friday, many of the mailboxes gaped open Saturday.

Rick Bowdren, inspector-in-charge of the Midwest division of the U.S. Postal Inspection Service, urged people across the Midwest to use caution in opening their mailboxes and recommended they tape them open so both homeowners and mail carriers could see what was inside.

David Holl, 44, who lives along a winding, wooded road northwest of Dubuque, Iowa, called the pipe bombs the work of cowards. His metal mailbox was blown apart Friday, and the letter carrier who opened it suffered injuries to his arm and hearing loss, authorities said.

"The biggest thought in my mind is why these cowards are preying on innocent people," Holl said. "Maybe they are trying to make some kind of statement, but they are sure doing it in the wrong way."

In Tipton, residents say they are a close community, despite the distance between driveways.

"This has really shaken all of us," said Rosemary Penningroth, a retired elementary school teacher who lives on a farm that's been in her husband's family for more than 55 years.

"I'm not really angry ... or panicky. But I don't feel nearly as secure as I did before," she said.

Danny Wagner, 42, a father of two boys, said it'll be months before he's comfortable letting his sons open the mailbox again.

"These kinds of things aren't supposed to happen in Tipton, Iowa," Wagner said. "It really changes your way of thinking."