Phoenix police have arrested three women believed to be involved in the largest counterfeit coupon scam in U.S. history.

The Phoenix Police Department, aided by the Coupon Information Corporation and some of the at least 40 wronged manufacturers, conducted an investigation to end the scam that police say has been operating for at least four years.

In the past four years, manufacturers became aware that copies of their coupons were being produced. They asked for the help of private investigators and the Coupon Information Corp. to find the source of the copies.

The investigation led them to Phoenix, where the properties of Robin Ramirez, Amiko Fountain, and Marilyn Johnson were raided Tuesday.

Investigators found $25 million in forged coupons in those raids. "That's $25 million worth of counterfeit just sitting around their daily operations on a random day. You have to wonder how much money passed through their business," said Bud Miller, executive director of Coupon Information Corp.

Police learned that Ramirez, who they consider the ringleader, had been mailing valid coupons to an international source that counterfeited mass quantities of them. The forged coupons were primarily sold on Ebay and her website, savvyshoppersite.com.

These coupons offered large discounts on products, even making some free, resulting in catastrophic losses for the manufacturers.

Police don't yet know how enormous those losses are, and probably won't for a while given the scale of this operation. Investigators found that Ramirez had at least four online accounts and 12 bank accounts.

"The Coupon Information Corp. says that manufacturers are losing tens of millions of dollars in coupon fraud. We're finding evidence that makes [Ramirez] a main player in this type of fraud," Holmes said.

Miller echoed how enormous this scam was. "Make no mistake, this was run as a business. These were not amateurs."

Ramirez is being held in jail on a $450,000 bond, while Fountain and Johnson have $250,000 bonds. None of the women have criminal records.

The charges they face include fraud, forgery, counterfeiting, and operating a criminal enterprise.