Guitar string maker D'Addario & Co. plans to open another factory in Suffolk County, executives said Thursday, as part of an ongoing expansion that has brought manufacturing jobs to Long Island from other states and China.

D'Addario, the world's largest manufacturer of strings and other musical instrument accessories, recently purchased 590 Smith St., an industrial building in East Farmingdale that is directly opposite its headquarters and main plant, and down the block from its new steel wire mill.

The family-owned company also plans to hire more engineers as it explores making plastic components locally rather than getting them from elsewhere in the country, James D'Addario, the company's chief executive, said.

"We do have plans for building out and expanding into other things here on Long Island," he said, and may "begin to look at injection molding some of these [instrument] accessories," he said.

The company employs 1,100 people, including 790 locally. The wire mill created about 30 jobs as a Massachusetts division shifted to Suffolk. The Massachusetts operation shut down Wednesday.

Of 590 Smith St., D'Addario said, "We'll probably do additional manufacturing in there. It's to be determined." Tenants in the 28,740-square-foot structure, including a coffee service and mixed martial arts studio, are expected to move out before year's end.

The building purchase, which property records value at $3 million, was helped by tax breaks from the Babylon Town Industrial Development Agency. In their application for $2.9 million in assistance over 15 years, D'Addario executives promised to hire 40 more workers and move the Pro Mark Drum Sticks division from Texas, according to IDA records.

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As part of the deal, Babylon also provided tax breaks for the company's headquarters and factory at 595 Smith St., and the wire mill at 540 Smith St.

Empire State Development gave $1.9 million in state tax credits toward the wire mill project, while the Suffolk IDA gave $755,565 to support improvements to 99 Marcus Dr. in Melville, where package printing and other work is done.

During a factory tour and ceremony with government officials Thursday, D'Addario said moving production of carbon steel wire from Massachusetts to Suffolk had aided the development of what he said is the world's strongest electric guitar strings, called NYXL.

The product was unveiled last night at the Guitar Center store in Carle Place with performances by guitarists including Vernon Reid and Earl Slick.

Noting that half of D'Addario's $150 million in sales come from overseas, Suffolk County Executive Steve Bellone said the company was proof that local factories "can compete, we can innovate."