The warning especially applies to anyone who may have mailed money over the past weekend.
Authorities say outside mailboxes were broken into at the Oradell Post Office Sunday night.
They say many pieces of mail were opened and a lot of checks were stolen.
Only some mail was recovered, including a number of holiday cards, and officials say they have no way of determining if a particular piece of mail was taken or not.
The US Postal Inspection Service is investigating the incident.
Customers are advised to:
--Contact your credit card company and bank if you dropped checks in any of the mailboxes
--Monitor your accounts
--At home, don't let mail accumulate
--If you use P.O. boxes, use them during the week and during they daytime hours
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