Improperly installed or faulty gaskets probably caused a recent spill of almost 500 gallons of caustic wastewater at a western Indiana facility where the deadly Cold War-era nerve agent VX is being destroyed, officials said Thursday.

Jeffrey Brubaker, the U.S. Army's project manager at the Newport Chemical Depot, said in a written statement that the spill occurred Oct. 29 . It was the third at the depot since operations began May 5. The earlier spills were blamed on faulty valves, which were replaced.