The company confirmed Friday a "visible leak" was found in December at the plant, The (New Orleans) Times-Picayune reported. Propylene was the chemical responsible for the explosion and fire Thursday that left two people dead and scores more injured.
Larry Bayer, who manages the plant in Geismar, also confirmed construction was under way near the site of the explosion with hundreds of additional workers at the plant, which was undergoing a major expansion.
The December incident led to the release of 514 pounds of propylene. The company is in negotiations with the Louisiana Department of Environmental Quality over penalties for previous leaks of propylene in 2008, the carcinogen benzene in 2009 and ethylene and volatile organic compounds in 2010.
The plant produces 80 million pounds of propylene and 1.3 billion pounds of ethylene every year. The chemicals, both derived from natural gas, are used to make plastics.
Williams Olefins, headquartered in Tulsa, Okla., operates a network of natural gas pipelines.