STORY: Bank shares fell on Tuesday after Moody's cut the credit ratings of several small- to mid-sized U.S. lenders, a move that further fueled fears that a banking crisis back in March may not be over.

Moody's cut the ratings of 10 banks by one notch and placed another six lenders, including Bank of New York Mellon, U.S. Bankcorp, and State Street on review for potential downgrades.

In a note, the ratings agency described worries about worsening profitability, a potentially mild U.S. recession, and risks in the banks' commercial real estate portfolios.

The cuts come after another ratings agency, Fitch, downgraded U.S. government debt from triple-A to double-A-plus.

Sam Stovall of CFRA Research told Reuters, "Moody's putting some banks on warning adds to Fitch's downgrade of the U.S. Treasury market last week and gives investors additional reason to be cautious..." adding, "it also means that the concern that we had in March over those three bank defaults, is not over yet."

The sudden collapse of Silicon Valley Bank and Signature Bank earlier this year sparked a crisis of confidence in the U.S. banking sector.

Those failures prompted a run on deposits at a host of regional banks despite authorities launching emergency measures to shore up confidence.