Responding to rapid growth, First Niagara Financial Group is opening a third mortgage processing center in downtown Syracuse to serve customers in its Central and Eastern New York markets.

The Buffalo-based owner of First Niagara Bank, which already employs 500 in the Syracuse region and operates 49 branches, will open its Central New York Mortgage Center in a former HSBC Bank USA facility on Washington Street next month, with at least 25 new full-time jobs. Those workers will join mortgage lenders the bank gained earlier this year through its purchase of HSBC’s upstate New York retail and small business banking operations.

The bank already has mortgage facilities in Buffalo and New Haven, Conn., but it said mortgage originations have soared 66 percent in the past year, with 85 percent coming through branches. Mortgage banking revenues soared 53 percent in the third quarter compared with a year earlier, and were up 2½ times for the first nine months of the year. First Niagara bought HSBC’s business in May.

“We are excited to continue our growth in Central New York, create new jobs and join in downtown Syracuse’s renaissance,” Senior Vice President Andy Fornarola said.

First Niagara, with $36 billion in assets and $28 billion in deposits, operates 432 branches and more than 400 ATMs in New York, Pennsylvania, Connecticut and Massachusetts.