Officials with the City of Fond du Lac say its Water Payment Portal has been hacked, and people who pay their water bill online through the system should check their credit card statements.

In a notice on the City of Fond du Lac's website, city officials say they were notified about the hack by a local partner bank on December 12 and an investigation is underway.

The city's third-party payment engine vendor stated there was a known vulnerability, which was addressed back in October.

However, city officials say there is a possibility that customers who paid their water bills online between August and October 2017 could have had their credit card numbers compromised.

City officials say during its investigation, they found the only data that has been skimmed is the credit card data and no other identifiable information has been skimmed.

Most purchases have been for small amounts at places like iTunes, Dunkin Donuts and other mobile/online payment portals.

The city took down the water payment system on December 13.

The notice also states that "this was a vulnerability in the third-party vendor. None of your credit card data is stored by the City of Fond du Lac."

City officials are encouraging customers who paid their water bills online between August and October to closely monitor their credit or debit cards.

At this time, the city is asking customers to pay their bills via mail, drop a payment in one of the city's drop boxes, or come to the city's office to pay.

The city also will accept a payment over the phone and will waive the $3.00 credit card fee.

The city also says if this issue causes any customers to pay their December water bill late, the city will waive the December late fee.