Hundreds of people in the Windsor, Ont., area say their debit cards were skimmed and their bank accounts raided by what police believe is a sophisticated crime ring based in Quebec.

Several debit machines at fast-food restaurants in the Windsor area were tampered with over the past few weeks, with thieves adding Bluetooth chips to the keypads. Windsor police suspect information about customers' accounts was then transmitted wirelessly to a car sitting in the parking lot.

Windsor police display a debit point-of-sale pin pad that has been tampered with. (CBC)They are now investigating 217 complaints, and losses are estimated in the hundreds of thousands of dollars. Police had a handful of cases last week, but calls started flooding in after the Family Day holiday weekend.

"People went to use them at a downtown bar and suddenly, 'I can't use my debit card anymore,'" Staff Sgt. Gerry Corriveau said.

One customer who tried to withdraw money from this bank machine on Drouillard Road contacted CBC News after he filed a police report.

"When I checked online I realized there were four transactions in my account," Daniel Keech said. "They totalled almost $1,000 that I did not make."

Even the head of a major financial institution fell victim.

"When I got home, I went to take a look, and yeah, there was a fraudulent transaction that had taken me up to the daily limit," said Charles Janisse, CEO of the Motor City Credit Union.

'It's much like a pickpocket'

Police said the fraudsters switched the pin pad and added a transmitting device at more than one local fast-food restaurant but would not say which ones.

"It's much like a pickpocket," said Corriveau, who explained the fraudsters go into a store and strike up a conversation with the clerk.

'They keep trying. But if we make it more difficult, bad guys don't get money.'— Staff Sgt. Gerry Corriveau, Windsor police

"They'll put a gym bag on the counter. It's a simple distraction technique. It's the same one that has been working with frauds forever. It's as simple as a three-card money trick."

Police said the suspects waited six weeks before striking, always withdrawing just under one of three limits: $200, $500 or $1,000.

Money withdrawn in Montreal area

Corriveau said many of the fraudulent transactions were made in the Quebec cities of Sherbrooke and Laval. Corriveau believes the suspects are part of an organized crime cell that travels up and down Highway 401, tampering with point-of-sale machines, then cleaning out customer accounts.

"Every time we lock the back door, they go to the front," he said. "We lock the front door, they go to the side door. They keep trying. But if we make it more difficult, bad guys don't get money."

The skimming was not limited to one financial institution, so all banks and credit unions across the city are issuing new cards to many of their customers.

"Even if your account was not compromised, your financial institution may change your card. just to be on the safe side," said Corriveau.

Scammed customers reimbursed

Police expect the number of cases to rise as banks send police their lists of affected customers. Police are advising residents to check their bank accounts, and merchants to either lock down or mark their pin pads, so they can't be switched without anyone noticing.

Individuals who are proven to be victims of fraud are protected under the Canadian Code of Practice for Consumer Debit Card Services and will be reimbursed by their financial institutions.

Banks refunded customers $104.5 million because of debit-card skimming in 2008, according to Interac Association.