Crowds queued at a cash machine in Manchester which gave double the amount of cash requested.
Word spread quickly about the error at the machine at the BP garage on Barton Road in Stretford on Thursday.
The giveaway went on for about six hours before the fault was reported to Nationwide building society.
The firm said it was "disappointing" that no-one reported it earlier. Those who took extra cash may now have to pay it back.
The machine gave £60 every time it was asked for £30, but also gave away more cash in different multiples depending on the money requested.