According to the company, the explosion occurred at 8:37 a.m. Central Daylight Time. Williams says it quickly isolated the unit affected, engaged emergency shut-down valves, and notified state and local authorities.
At the time of its statement, Williams was unsure of the extent of casualties at the plant, and was still accounting for its personnel. Subsequent news reports confirm that at least one plant employee was killed in the explosion, with dozens more injured.
The plant in question produced olefins, a class of hydrocarbons that includes ethylene and propylene, which are used to produce polymers for plastics (e.g. polyethylene and polypropylene). Other olefins-based petrochemicals include ethylene dichloride, ethylene oxide, propylene oxide, oxo alcohol, polystyrene, and acrylonitrile.
The Geismar plant is responsible for producing as much as 1.3 billion pounds of ethylene, and 90 million pounds of polymer grade propylene annually.