NEW YORK (CNNMoney.com) - A sophisticated group of thieves used technical trickery to steal ATM card information -- and over $100,000 -- from customers at two New York City Washington Mutual branches.

The thieves rigged fake keypads and bank-card slots onto ATMs to gather card information and encoded the information on new cards, police say.

Fake keypads and card slots used by thieves to take banking information and steal money from victims' bank accounts.

Surveillance photo of one suspect in the ATM thefts.

They then used the new, fraudulent cards for withdrawals from approximately 50 Washington Mutual accounts at other ATM locations.

The two Washington Mutual branches were on Canal Street in lower Manhattan and on Hylan Boulevard on Staten Island.

Images of the suspects were recorded on the bank's security cameras.

"This is a very unusual crime because of the sophistication it requires," said John Hall of the American Bankers Association. "The ATM system is hard to compromise because it requires two separate keys -- the card and the PIN -- and PINs are especially hard to get."

Hall said that ATM fraud was more common at non-bank ATMs, where the security is less sophisticated.

The Electronic Funds Transfer Association, an industry trade group, has worked to secure ATM transactions for years, including requiring extensive background checks for non-bank ATM operators.

Washington Mutual said it was cooperating with local and federal law enforcement agents in the investigation.

The bank encouraged customers to review their account transactions and balances and to contact them promptly if any unauthorized transactions were found. Washington Mutual can be reached at 1-800-788-7000.

Consumers are protected against bank fraud, and will be eligible for a complete refund when the bank finds that the transactions were illegal. Banks typically offer the aggrieved customer a line of credit until the charges can be proved.

Police said ATM users should be aware of banking equipment with loose wires or odd-looking equipment, video cameras trained on cards and keypads that no longer have Braille markings.

They also encourage people to try to use the same ATM for most of their transactions so they can better recognize when something is different.

In addition, security experts advise that you never let ATM or other cards out of your sight at banks, restaurants and other locations where somebody might be able to copy the number.

The New York Police Department is requesting the public's assistance in identifying the suspects in the WaMu case, who remain at large.

Anyone with information about suspects is asked to call the NYPD Crimestopper hotline at 1-800-577-TIPS (1-800-577-8477).

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As if the thefts weren't bad news enough, ATM fees are at a record high. Read the full story here.

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