India, March 20 -- Investors were left scratching their heads on Thursday after the abrupt resignation of HDFC Bank chairman Atanu Chakraborty the previous night, while shares of India's largest private sector lender plunged 5%.

Despite the strong words from the exiting chairman, analysts do not expect any material irregularities at the bank, while attention turns to the reappointment of chief executive Sashidhar Jagdishan.

An investor at the bank's conference call on Thursday morning summed up the exasperation: "So far, whatever I have heard on this call doesn't make me any wiser than I was an hour ago." Late on Wednesday, HDFC Bank released Chakraborty's resignation letter, in which he wrote of "happenings and practices within the ban...