Shares of BlackRock (BLK) fell sharply on Wednesday after the global investment management firm confirmed it would commence a secondary offering of 42 million shares of its common stock.

Bank of America, (BAC) BlackRock's largest shareholder, and PNC Financial Services Group (PNC), which owned BlackRock before it went public and is currently its second largest shareholder, will offer some of their shares in the sale. Bank of America will sell 34.5 million shares and PNC will sell 7.5 million.

The offering could represent the continued efforts of the banks to bolster their balance sheets by selling off assets. In a statement, BlackRock said it would not receive any proceeds from the sale of the shares.

On the news, shares of BlackRock declined to as low as $164.01 in early morning trading, more than $9 off the stock's Tuesday closing price of $173.04.