NEW YORK (CBSNewYork) — A construction worker was killed Tuesday when a steel joist intended for the green roof at the Barclays Center fell off and hit him.

The worker, whose name has not been identified, was part of a team installing the environmentally-friendly roof when the joists rolled off the truck before they were fastened to a crane to hoist them into place, sources told 1010 WINS.

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The worker, whose identity has not been released, was struck by one or more of the joists as they fell off the truck, sources said.

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The worker was employed by steel erector contractor the James F. Stearns Company, a subcontractor of Bankers Steel, which is working with the construction manager for the green roof installation, sources said.

In a statement, Greenland Forest City Partners – the development venture behind the Barclays Center – said the accident was under investigation.

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“All of us at Greenland Forest City Ratner Partners and Barclays Center extend our most heart-felt condolences to the worker’s family and friends,” the firm said. “We are currently working with all relevant agencies to determine what caused this terrible tragedy.”