The fake bills matched the description of others passed earlier at the mall at JC Penney and Payless Shoes, which led to the arrest of a Martinsburg, W.Va., man.
Counterfeit bills were also passed at the mall around the holidays and the Washington County Sheriff's Department is trying to determine whether there's any connection.
The recent incidents at Valley Mall aren't the first reports of counterfeit bills that have circulated in the area.
In early January, nine phony $100 bills, described as "high quality," were passed at Wal-Mart and one at Sears in Martinsburg, W.Va., according to Martinsburg City Police.
Last week, in neighboring Allegheny County, Maryland State Police recovered three counterfeit bills - two $20 bills and a $50 bill - passed at local businesses, including one at the drive-up window at a McDonald's restaurant in La Vale, Md.
"The counterfeit bills being used in these cases are very obvious when examined and handled," police said.
Though you don't have to be an expert to notice the bills are fake, the people passing the bills are targeting places that are busy and where cashiers have to handle money quickly, said a U.S. Secret Service agent who is investigating the recent incidents and would not give his name.
The Secret Service, in addition to duties protecting the president, is the law enforcement arm of the Treasury Department.
"If you saw them you'd know they're bad. But at a quick glance, they're good enough to get by," he said.
It's a federal offense to pass counterfeit money, punishable by a maximum prison sentence of 10 years, the agent said.
Rickie Lee Nash, 30, of 406 S. Kentucky Ave., Martinsburg, arrested in January, was charged with two counts of presenting counterfeit U.S. currency, two counts of theft under $300 and one count of theft scheme under $300, according to the sheriff's department.
Most banks and some businesses have a counterfeit detector which looks like a highlighting pen. A mark turns one color if the bills are real and another if the money is fake.
The counterfeit bill doesn't have the magnetic strip embedded into the fibers, or the telltale ridges across the bottom of the portrait that are obvious to the touch.
To help protect U.S. currency, the Treasury Department recently issued new $100 and $50 bills with enhanced security features, including a polymer thread embedded in the paper that indicates the note's denomination by its position.
Other security measures on the new bills include micro printing, watermarks, concentric fine lines and color-shifting ink, according to the Treasury Department.
Local merchants are being asked to contact the state or local police if any suspicious bills are passed at their establishments.