Officials said the string of thefts is happening in Eugene neighborhoods with locked boxes that hold mail and packages for multiple residents.
U.S. Postal Inspector Dennis Fernald said if you're a victim of mail theft you should monitor your bank accounts and report any fraudulent activity.
"People should try not to leave their mail in their mail boxes overnight. They should try to retrieve their mail out of their mail boxes as soon as possible, obviously within reason," said Fernald.
Officials say to take your outgoing mail to the post office or to a blue collection box to be safe.
Any victims of theft are asked to contact the United States Postal Inspection Service or local police.
Officials said the thefts have happened in ZIP codes for 97401, 97402, 97404 and 97408.
If you have any information regarding these thefts, please contact the U.S. Postal Inspection Service or the Eugene Police Department at the following numbers:
Brendan Soennecken - 503-719-2087
Dennis Fernald - 503-793-0176
Eugene Police Dept - 541-682-5111