A technical fault with bank machines allowed people with no money to withdraw funds.
Irish bank Bank of Ireland apologised on Wednesday after a technical problem allowed customers to withdraw or transfer more money from their accounts than they actually had.
The problem led to queues outside cash machines across the country on Tuesday and into the night, as rumours spread that the machines were being used to withdraw 'free' money, and police were forced to intervene.
Some reports in the Irish media said that customers with no money in their accounts were able to withdraw up to €1,000.
Bank of Ireland warned users of ATMs and financial apps that money taken out would eventually be debited from people's accounts.
"We sincerely apologise for the disruption caused by this outage. We know that we have failed to provide the level of service that our customers expect of us", the bank continued.
Ireland's Finance Minister Michael McGrath said he has asked the country's central bank to investigate the matter.
"Disruption to banking services can have a significant effect on people's personal lives and on the running of businesses," he said. "Customers rightly have an expectation of a high quality of service and to be able to have uninterrupted access to services."
Ireland's central bank has already fined Bank of Ireland for flaws in its IT systems, and has said it is monitoring the implications of this incident.
Brendan Burgess, founder of the AskAboutMoney.com website, told broadcaster RTE the bank needs to improve its "clunky" IT system.
However, he felt that "if you know you have no money but you take €1,000 from a bank account, that's fraud. And that's not a problem that has anything to do with Bank of Ireland's systems".