Hamilton is scrambling to get more information about a potential data breach that revealed customers' names, addresses and roll numbers from their water bills.

The city said Wednesday that there was a potential leak of information through Alectra Utilities, which handles water billing for about 150,000 customers on behalf of the city, regarding an unknown number of customers.

City staff discovered the potential breach, said Mayor Fred Eisenberger, and notified Alectra. Now the city will notify all affected customers and bill Alectra for the cost.

In a statement emailed to CBC, the utility said it is "working closely" with the city to "resolve this matter to their satisfaction."

Spokesperson John Friesen said Alectra is not aware of "any information being compromised" at this point.

Eisenberger said the breach may have originated off shore. City programmers were doing work and realized that some of Alectra's third party vendors may have access to information without the appropriate approval.

The city says it hasn't confirmed that a privacy breach has occurred, or that the information was used for a reason other than delivering water services. But the public is being advised to maintain its "normal level of vigilance" when it comes to personal information.

"This is kind of a precautionary forewarning," he said. "City staff is still trying to come to an understanding of who and how many. What we do know is what might have been released which is the municipal tax roll number, name and address. Very low level stuff."

City council received a staff report this afternoon, and all but Eisenberger and Coun. John-Paul Danko voted to make the report public.

The city is also notifying the Information and Privacy Commissioner of Ontario (IPC).

Friesen said the utility will "cooperate fully" with any investigation by the IPC, adding the company's own privacy officer has also been engaged.

Concerned customers can call Alectra by calling 905-317-4781 or emailing PrivacyOfficer@alectrautilities.com.