Cathay General Bancorp said late Monday that it has begun a secondary public offering of its common stock, with expected gross proceeds of up to $70.5 million.

The Los Angeles parent of Cathay Bank said it granted the underwriter, BofA Merrill Lynch, a 30-day option to purchase up to an additional $10.5 million of its common stock to cover over-allotments.

The bank holding company, which now has about 53.1 million shares outstanding, did not state how many new shares were issued. But based on Monday’s closing price around 9.9 million shares are expected to be sold, including the over-allotment.

The press release did not indicate how Cathay intended to use the proceeds. However, several other community banks in Los Angeles have recently sold shares to either bolster capital, make acquisitions or pay back government TARP funding.

Cathay shares closed down 11 cents, or 1 percent, to $9.07 on the Nasdaq.