A Halifax worker has been arrested on suspicion of stealing around £700,000 from the bank's cash machines.
Local police were called in following an internal investigation into the missing money at a branch in Redditch, Worcestershire.
A 25-year-old man was arrested on suspicion of theft, fraud and money laundering and has been released on bail until October.
A police spokesman told the Redditch Advertiser: "The arrest relates to an allegation that around £700,000 had been taken from an account used to supply funds to an ATM machine at the town's Halifax branch between September 2011 and July 2012."