A debit card scam that struck self-checkout lanes at 20 supermarkets across the Bay Area hit Petaluma over the weekend.

Customers and employees at a Lucky Supermarket at the Petaluma Gateway Center on Lakeville Highway reported as much as $1,000 withdrawn from accounts linked to their ATM cards.

Police were investigating whether the withdrawals were linked to a known security breach in the chain's self-checkout system.

Seven people reported that money was withdrawn from their bank accounts connected to ATM cards and police are investigating whether the Lucky machines are involved, Petaluma Police Sgt. Steve Nelson said. The amount lost averaged about $500.

The thief or thieves appeared to have withdrawn the cash from locations on the San Francisco peninsula and Southern California, he said.

Two employees at the Petaluma Lucky Supermarket reported losing as much as $1,000 to unidentified sources that withdrew money from their accounts after they used the self checkout scanners.

The employees declined to give their names because they feared they could be fired for talking publicly about the scheme that targeted their employer.

One employee said the company on Friday replaced the swipe machines used in the grocery's self-checkout area.

"They jumped right on it," the employee said.

on Sunday evening, numerous customers were using their ATM cards at the self check-out line. David Ortega, a Petaluma mechanic, bought a loaf of bread and a few other groceries at the self-checkout line, and said there were no warnings or any other notices posted about using his ATM card.

"I'm am clueless," said Ortega, 40.

Store employees had been warning customers not to use their ATM cards at the self-checkout line, but stopped because the store considers the problem resolved, one employee said.

Lucky Supermarket officials issued a warning to customers on Nov. 23 that "skimming" devices were found at 20 of their Bay Area stores, none in the North Bay.

The devices can be inserted in or above an existing ATM slot or card reader, and can gather account information and in some cases PIN numbers from users.

Officials at the time said in a statement that "We are not aware nor have we been notified of any reports that customer accounts were compromised."

Lucky officials Sunday told police they would add Petaluma's Gateway Center branch to the list of stores struck by the scheme, police said..

Lucky officials previously said the scheme was discovered during "regular store maintenance."

"Be careful where you're using your card until we can figure out where this is coming from," Nelson said.