The First of Long Island Corp., based in Glen Head, said Monday that its first-quarter net income rose 19 percent to $9.1 million.

The bank said assets rose 11.5 percent in the last 12 months to $3.6 billion. Residential mortgages rose 27 percent in that period to $1.36 billion.

Residential mortgages “are a nice way for us to diversify our loan portfolio, because we are a commercial bank,” said Mark D. Curtis, chief financial officer at First of Long Island. “Diversifying makes sense from a risk perspective.”

The company, parent of First National Bank of Long Island, said in a statement it expects to continue to grow loans and deposits through new products and branches.

The bank, which has 47 branches, expects to open four more locations in the next year. One of those branches will be in East Setauket. The other three will be in Brooklyn or Queens.

First of Long Island has three branches in Queens and one in Brooklyn.

“Queens and Brooklyn have a large concentration of our target markets of consumer lending and small businesses,” Curtis said.

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First of Long Island shares rose 2.21 percent on Monday to $27.80. Its shares are up 36 percent in the last year.