Employees called 911 about 8 a.m. Thursday to report the burglary, Sultan Police Chief Jeff Brand said.
Investigators believe that someone broke in through an employee area in the back between 6 p.m. Wednesday and this morning, he said.
Several items were thrown around and damaged, Brand said. Some packages also were opened.
"Because of the disarray, it is difficult to inventory the losses right now," he said.
The Snohomish County Sheriff's Office and the U.S. Postal Service also are investigating.
Anyone with information should call 425-388-6260. Tipsters can be anonymous.
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