US prosecutors are investigating the collapse of Silicon Valley Bank after a dramatic outflow of customer deposits from the Californian tech lender led to the biggest US bank failure since the global financial crisis, according to a person familiar with the matter.

The Securities and Exchange Commission has also launched an investigation into the lender’s collapse, according to media reports. The investigations, which were first reported by The Wall Street Journal, include looking into stock sales made by SVB staff in the days leading up to the lender’s fall, the reports said.

On February 27, less than two weeks before regulators closed SVB, Gregory Becker, the bank’s chief executive, exercised options on 12,451 shares at a cost of $105.18 and immediately sold them at prices ranging from $285.27 to $289.05, according to SEC filings. SVB’s chief financial officer Daniel Beck sold 2,000 shares at $287.59 on the same day, documents show.