Officials say staffers are using counterfeit detector pens to ID fake bills printed on copier paper, not cotton-and-linen-fiber paper used by the government. A mark placed on the bill turns black if counterfeit paper has been used.
The Houston Chronicle reported Thursday that city libraries for about a month have been checking all bills larger than $1.
Spokeswoman Sandra Fernandez says all 42 library sites were already checking all bills $20 and above. Fernandez says library financial officials decided to change the policy after the discovery of some phony smaller bills.
Authorities did not release an estimate on how much fake cash has tried to be passed at Houston libraries.