Health-care fraud costs taxpayers billions of dollars every year, with con artists constantly finding new ways to cheat the system. And while federal investigators report they are trying their best to crack down on crime, one scheme involving pharmacies and Medicaid is growing so quickly they said they can't work fast enough to keep up.

Here's how the scam works, according to Tom O'Donnell, special agent in charge with the Health and Human Services Office of Inspector General: An owner of a pharmacy asks customers to bring in prescription slips from doctors. But instead of filling the scripts and dispensing the drugs, the owner pays the customers a small fee and then bills Medicaid for the drugs that were never dispensed.