After a comprehensive review of banks in the eurozone, regulators say that 25 banks out of 130 had a capital shortfall that would expose them to severe problems in an economic crisis.

The European Central Bank released the results of its yearlong study Sunday, putting banks on notice to boost their reserves within 9 months. Officials say many banks have begun that process — and some of them have already made up the shortfall that's based on a snapshot of data taken last December.

All together, the shortfall was measured at €24.6 billion, or around $31.2 billion. Several banks with the largest shortfalls are based in Italy and Greece.

The number of banks that flunked the stress test was slightly higher than what analysts had predicted, according to the Wall Street Journal. But as they released their data in Germany today, ECB officials said that their findings should reassure investors.

"This unprecedented in-depth review of the largest banks' positions will boost public confidence in the banking sector," said ECB vice president Vítor Constâncio. "By identifying problems and risks, it will help repair balance sheets and make the banks more resilient and robust. This should facilitate more lending in Europe, which will help economic growth."

The ECB says that the 130 credit institutions included in the exercise had total assets of €22 trillion, or nearly $27.9 trillion.

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