Moody’s Investors Service Monday cuts its view on the United States banking system from stable to negative, and flagged six banks, CNBC reports.

Following the collapse of Silicon Valley Bank, Moody's has put the following banks on review: First Republic Bank (FRC), Zions (ZION), Western Alliance (WAL), Comerica (CMA), UMB Financial (UMBF) and Intrust Financial.

"Today's rating action reflects First Republic Bank's high reliance on more confidence-sensitive uninsured deposit funding, its high amount of unrealized losses in available-for-sale and held-to-maturity securities portfolios, as well as a low level of capitalization relative to peerds," Moody's said.

As for the credit rating agency dealing a harsh blow to the already-reeling banking sector, Moody's cited a “rapidly deteriorating operating environment.”

Moody’s said it was downgrading the U.S. banking sector due to three key bank failures that necessitated regulators stepping in to rescue depositors.

“We have changed to negative from stable our outlook on the U.S. banking system to reflect the rapid deterioration in the operating environment following deposit runs at Silicon Valley Bank (SVB), Silvergate Bank and Signature Bank (SNY) and the failures of SVB and SNY,” Moody’s report said.

Moody's is one of three major credit ratings agencies in the U.S., the other two being FitchRatings and Standard & Poor's.