Amsterdam city council is working to find out why almost 10,000 households were wrongly paid thousands of euros in extra housing benefit, costing the city €188m.

City alderman Pieter Hilhorst has commissioned an external agency to look at the cause of the wrong payments, which led to some people expecting a €155 payment to receive €15,500 instead. The highest wrong payment was €34,000, according to the Parool.

In a letter to people who were sent the extra cash, the council says it deeply regrets the error but points out people will have to pay the money back.

Officials have already reversed as many payments as possible, news agency ANP said.

However, some people had already transferred the money to a different bank account or spent it. They are now overdrawn, presenting an extra headache to council officials, the Parool reported on Monday.