Bank of America Corp. mopped up more than $15 billion in new deposits in a matter of days, emerging as one of the big winners after the collapse of three smaller banks dented confidence in the safety of regional lenders.

The inflows offer a first glimpse into the deluge of deposits that made its way to the country’s largest banks as customers fearful of a spreading crisis sought refuge in the firms seen as too big to fail. The money flowing into the second-largest US bank was described by people with direct knowledge of the matter, who asked not to be identified as the information isn’t public.