US Senator Elizabeth Warren, who is pushing tighter banking regulation, has called for an investigation into the failures of Silicon Valley Bank and Signature Bank, the Wall Street Journal reported on Sunday.

Warren sent a letter to the inspectors general of the Treasury Department, the Federal Deposit Insurance Corp and the Federal Reserve on Sunday, urging regulators to examine the management and oversight of the banks ahead of their collapses this month.

She said preliminary results from the investigation should be provided within 30 days, the newspaper reported.

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“The bank’s executives, who took unnecessary risks or failed to hedge against entirely foreseeable threats, must be held accountable for these failures.

But this mismanagement was allowed to occur because of a series of failures by lawmakers and regulators,“ the report quoted Warren as writing.