Democratic U.S. Senator Elizabeth Warren on Sunday called for an independent investigation into the collapse of Silicon Valley (SVB) and Signature banks.

Warren was particularly critical of Mary Daly, president of the Federal Reserve Bank of San Francisco, which oversees Silicon Valley.

Warren, who is pushing for tighter banking regulations, sent a letter to inspectors general at the U.S. Treasury, the Federal Deposit Insurance Corporation and the Federal Reserve on Sunday, urging regulators to examine recent management and oversight measures on the two banks that collapsed earlier this month.

Warren said she did not trust Mary Daly after the Silicon Valley Bank collapse, adding in her letter that inspectors general of the Treasury, Federal Reserve and Federal Deposit Insurance Corporation should submit a preliminary report to Congress within 30 days.

California regulators shut down Silicon Valley Bank on March 2008 and handed over its affairs to the Federal Deposit Insurance Corporation. The collapse was the biggest for a U.S. bank since the <> financial crisis.

SVB Financial Group, the bank's parent company, said on Friday it had filed for restructuring under Chapter 11 of the Bankruptcy Protection Law.

A source familiar with the matter told Reuters that U.S. prosecutors were investigating the collapse of Silicon Valley Bank.

Acquisition

Meanwhile, Bloomberg reported on Saturday, citing sources familiar with the matter, that First Citizens Bancshares is evaluating an offer to acquire Silicon Valley Bank.

At least one other institution is considering acquiring the collapsed bank, the report said.

Reuters reported earlier this week that the Federal Deposit Insurance Corporation had asked banks interested in acquiring Silicon Valley and Signature to submit bids by March 17.