CLAYTON, Mo. – Police say mail carriers are being targeted by criminals who want your money. They’re looking for universal mailbox keys, so they can steal your money, but they’re suddenly failing to get those keys.

Clayton police report an attempted robbery Tuesday of a mail carrier on Ridgmoor Drive, just North of Clayton Road.

Detectives say the robber was looking for the carrier’s universal key – known as an “arrow” key. It’s a key that can access USPS collection boxes and cluster mailboxes.

Clayton Police said the robber did not get an arrow key – and that a similar robbery attempt also failed in North County soon after. The Department warned in an alert that criminals are trying to steal keys so they can pilfer mail and snatch checks that they intend to alter & deposit fraudulently.

But now the bad guys are in for a surprise. We’ve learned of new mail security measures that are leaving the criminals empty handed.

Federal investigators are now involved. We spotted them canvassing the quiet Clayton neighborhood. Sources tell us robbers are not getting the master keys they’re hoping for because of a recent top secret security change by the postal service that makes it impossible.

Investigators are taking the attempted robberies seriously, however, because of a fear over a possible trigger-happy criminal who may not understand the mailman no longer has what they want.

Federal investigators have been busy, with eleven defendants just this year who have been charged or pleaded guilty to mail related crimes. A federal case in September involved a suspect who was unable to get a mailbox key. His attempt alone could still come with a 15-year prison sentence.