Thunder Bay Hydro is warning customers that a scam already noted by authorities in the U-S has turned up in the city.

Fraudsters are phoning customers claiming to be from the company's "termination department", said Thunder Bay Hydro spokesperson Eileen Dias.

They threaten to cut off the power if a payment isn't made through pre-paid credit cards or wire transfers.

Dias said people could be fooled, because Thunder Bay Hydro does contact customers by phone.

"These criminals are using very similar methods that a utility would use in order to connect with a customer in a delinquent situation," she said.

Scam is 'sweeping' the U.S.

Thunder Bay Hydro knew the scam had hit the city when the company received concerned calls on Wednesday from three different businesses within an hour.

The Better Business Bureau in the United States said the scam is "sweeping" the country and originated in Connecticut.

"The amount of money being extorted ranges from several hundred to several thousand dollars," it said in a news release.

The bureau also noted that scammers can seem legitimate because they may have collected information from other sources.

Customers getting a call they know is not from the utility should get as many details as possible, then call police, Dias said.