A water company that serves thousands of Long Island residents is under investigation by the state for a mistake that cost its customers.

New York American Water Company says it discovered what it called an "accounting error" that overvalued properties in the Sea Cliff area. Correcting that error means customers will see a 34 percent reduction to their bills.

The Department of Public Service says they are reviewing to "ensure that any property tax overpayments are not in any way paid for by customers and will determine whether customer refunds are due." They are also investigating whether other subsidiaries of American Water were affected by the error. 

Although some residents are pleased to hear their water bills will go down, they told News 12 they want the state to do more. Some say they would like the governor to condemn American Water and have the Jericho Water District take over.

"If that's what needs to be done so they're not taking advantage of the citizens here, I'm for it," says David Weinberger, of Sea Cliff. 

Sea Cliff water customers will see their water bill drop starting in January.

American Water said in a statement that not only did it notify the Public Service Commission of their error, but it also submitted a plan to "safeguard its customers from financial harm."