A gas and electric utility is warning customers to be aware of scammers posing as utility employees.

The Green Bay-based Wisconsin Public Service said the scammers have been contacting small businesses and residential WPS customers and telling them payments on their accounts have not been received. Customers are told their power could be disconnected immediately if they don't make a payment within an hour or two.

"A major red flag in this scam is that customers were told to purchase prepaid debit cards and then call back to make payment," WPS said in a statement on its website. The company said it would never require that method to make account payments.

Another scam is that customers are told to get some cash together for pickup.

The utility company urged customers who have been contacted by a suspected scammer to call police.

WPS is an electric and natural gas utility headquartered in Green Bay serving northeastern Wisconsin and part of Upper Michigan.