DES MOINES, Iowa (AP) - A federal official is warning Iowans to be watchful when opening their mailboxes.

That's because various homemade bombs have damaged mailboxes throughout the state.

U.S. Postal Inspector Sam Owens says as many as 20 incidents have happened around Iowa over the past month. No injuries have been reported.

Most of the mailbox bomb incidents were in Clay County, where five juveniles were charged and are awaiting trial.

Four soda pop bottle bombs also were found in Des Moines mailboxes this month.

Authorities say they have suspects lined up in connection with two mailbox bombs in Cedar Falls, where they believe model rockets were used to make the devices.

Officials don't think the incidents are related.