At least seven businesses in the Xenia, Ohio, area have been snookered by counterfeiters who have used bleach to turn $5 bills into phony $100s, Police have said.

Business owners were warned to check carefully any $100 bills they receive, by holding them up to the light rather than relying on the standard marking-pen test.

Todd Bagby, resident Secret Service agent in Dayton, told the Dayton (Ohio) Daily News, "Anytime you get a $100 bill, just put it up to the light because you're going to see the watermark or portrait of Abraham Lincoln where it should be Benjamin Franklin. This is another good reason why you can't rely on the pen alone."

The bogus bills began turning up in Greene and Montgomery Counties early this month, and have typically been used to make a purchase at stores or restaurants.

Phony bills in the region are usually $20 bills while $100s are rare, Xenia Police Capt. Scott Anger told the Daily News.