For about six days in late May to early June, PSE&G, a utility company in New Jersey, noted customers were trying to or did pay their bills with the fake routing number and the payment bounced back because it was not a legitimate way to pay.
Bonnie Sheppard, spokeswoman from PSE&G in New Jersey, said about 10,000 customers tried to pay their bill with the scam "credit."
The company, which serves three-quarters of New Jersey's population, has over 2 million electric customers and nearly 2 million gas customers.
While customers in Iowa have mostly been contacted by telephone, victims have unwittingly encouraged their friends to join in the scheme by social media and word of mouth, said Potthoff of MidAmerican Energy.
"People think they are getting a good deal but they are publicizing a scam," Potthoff said.