SPRINGFIELD, Ohio (AP) -- Federal investigators have determined the likely cause of the 2011 Ohio crash of a Wright Brothers biplane replica that killed two volunteer pilots.

The Dayton Daily News ( http://bit.ly/VrAgKZ ) reports that the crash of the Wright "B" Flyer probably happened because of a failed propeller shaft weld that resulted in a loss of engine thrust during the test flight.

The two experienced pilots died when the plane, dubbed "Silver Bird," crashed about 3 miles from an airport in Springfield where they had taken off on July 30, 2011. Springfield is about 45 miles west of Columbus.

A probable cause report released this week by the National Transportation Safety Board said the left propeller shaft had a broken weld, which would have prevented the left propeller from being driven by the engine.

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Information from: Dayton Daily News, http://www.daytondailynews.com