Three phony bills in denominations of $20, $50 and $100 have been passed during the last two weeks.
The U.S. Secret Service has been asked to investigate.
Two counterfeit bills were used in the city of Snohomish between March 20 and 22.
The first one — the $20 bill — was used at a downtown store.
"It had a weathered look to it," Snohomish Police Chief John Flood said. "They tried to make it look like it had been around the block a few times."
A fake $50 bill was used at a gas station and convenience store in the north end of town. Flaws were apparent under close inspection.
"The size was incorrect," Flood said. "It was smaller than a real $50 and the paper felt different."
The bad $100 bill was used at a McDonalds off 128th Street south of Everett on Sunday.
Police don't have a firm suspect, but are trying to identify a man in his mid 20s to early 30s they believe used at least one of the counterfeit bills. He is white and reportedly was driving a gray Nissan Pathfinder.
Flood said he hopes people and businesses will be vigilant.
There are precautions that can be taken.
If a bill looks suspicious, compare it to another bill. Look for tiny red and blue fibers embedded in the paper.
Examine the serial numbers to make sure that they all match and are evenly spaced.
Look for a security thread running from top to bottom.
Keep a counterfeit detection pen near the cash register. They contain an iodine solution that creates a black mark on counterfeit bills.
For more information, go to http://1.usa.gov/1pFaXCU.
Eric Stevick: 425-339-3446; firstname.lastname@example.org.
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