THIEVES are using card skimmers as slim as half a centimetre to read the electronic information on debit cards as they are inserted into automatic teller machines (ATMs).

NSW Fraud Squad Detective Sergeant Peter Meagher said thieves were coupling the devices with small hidden cameras placed above the machines.

The cameras record PINs as users punch them in.

Armed with the numbers and electronic data, thieves have all the information they need to make fake cards and strip victims' bank accounts of funds.

Sergeant Meagher said he and his team were investigating the latest attempted card scam at Cronulla, as well as five other cases across Sydney this year.

Police were called to the ANZ Bank's ATM in the Cronulla Street Mall on Saturday, April 12 after a card skimmer was found attached to it.

A man alerted authorities when the device broke off while he was using the machine.

Sergeant Meagher said police had removed the device and ANZ customers who used the machine were not at risk of being robbed.

"Unless you have both devices, the card skimmer and the camera, the information on either device isn't of any use," he said.

Sergeant Meagher said thieves in some parts of Australia were beginning to replace cameras with false keypads which could record PINs being entered by card users while the ATM continued to operate as normal.

He warned bank customers to familiarise themselves with the appearance of the ATM they usually used.

"If you notice anything that is abnormal or different about it, report it to the bank or police immediately," he said.

He added that ATM users should cover their hands while punching in their PIN to prevent it being recorded by a hidden camera.