First Niagara Financial Group is once again expanding in the Larkin District, taking up 40,000 square feet on the seventh floor of the district’s Larkin at Exchange Building after it was vacated by Capital Management Services a few months ago.

The Buffalo-based owner of First Niagara Bank will fill the former Capital Management call center by the end of the first quarter, quickly ensuring that the flagship Larkin Building won’t have a big vacancy for long. The bank already occupies some space on the seventh floor, and will now take up the entire floor, comprising about 60,000 square feet.

That means, in total, it will occupy most of the sixth floor, then all of the seventh and ninth floors at Larkin, plus the nearby Larkin U Building, giving it a total of 236,709 square feet, or enough space for 886 “seats,” said spokeswoman Jodi Johnston.

“This move enables us to address the space limitations we’ve experienced, based on our growth to date, and allows us to reconfigure our existing space to enhance collaboration in the workplace.”

She said the bank had agreed in advance to lease the added space as soon as officials learned it would become available, anticipating it would be needed. “We found that with each acquisition, we added to our Buffalo employment base,” she said. “Now we have the opportunity for future growth at Larkin.”

Capital Management, a collections firm, moved out of Larkin last fall after the local firm’s owners paid $4.6 million to buy the South Ogden Street Plaza, a neighborhood retail strip plaza at 652 and 690 S. Ogden St. at Dingens Street. The plaza’s big tenants include Big Lots, Wendy’s restaurant, CVS Pharmacy and Family Dollar.

The 114,280-square-foot plaza, which sits on 11 acres, is already home to a credit card processing subsidiary of Capital Management called Center One Capital LLC, and company executives felt it made more sense to consolidate operations at the larger plaza.

Howard Zemsky, managing partner of Larkin Development Group, which owns the Larkin Building, said the departure “was very cordial and very much of mutual consent, as we knew First Niagara was looking for more space and Capital had the opportunity to consolidate at and acquire the plaza.”

Capital Management retains its headquarters and administrative functions such as accounting and legal on the 10th floor of the Larkin Building. “We loved the space in Larkin. We love Howard Zemsky,” said Larry Costa, executive vice president of business development at Capital Management. “This had nothing to do with that.”

Founded in 2000, Capital Management employs more than 1,000, with other offices in Las Vegas and New Delhi, India. Costa said the firm is still growing.