For the second time in six months, a Winnetka bank branch ATM was outfitted with a device to steal customers’ personal information.

Technicians working on the ATM at Harris Bank, 1070 Gage St., discovered a “skimming device” at 10:56 a.m. May 19, according to a Winnetka police report.

“A very low, small number of customers were compromised,” said Patrick O’Herlihy, Harris Bank spokesman. He declined to say the exact number of people whose accounts were breached, but said they were all reimbursed and provided new debit cards.

O’Herlihy said the device was installed at 7 a.m. May 19, according to surveillance video. Investigators also discovered by watching video that a device had been installed May 18 at the same ATM machine, but had been removed later that day, he said.

The same Winnetka bank branch reported an ATM skimming device in December in which 25 customer bank cards were swiped. Not all of the customers’ accounts were compromised, O’Herlihy said at the time.

In that case, the skimming device had been attached over the weekend — from Sept. 25-26 — but bank officials learned of the incident on Nov. 22 when a string of unauthorized bank transactions took place, O’Herlihy said at the time.

On Monday, O’Herlihy said there’s nothing particularly inviting to criminals about the ATM at 1070 Gage St.

“I think it’s not a question of this ATM. I think it’s a question of skimming in general,” he said. “It’s an industry issue.”

Winnetka Interim Police Chief Patrick Kreis said in December that ATM skimming devices are becoming more common as technology advances.

“When they’re installed, they tend to involve the use of a façade front of a portion of the machine that is stuck on the face of the ATM,” Kreis said. “It replicates the insert card device. What happens is the device is actually reading the account’s magnetic information from the card and recording the (personal identification) number that is being attempted to be used.”

The machine would store the information for later use.