He said authorities are investigating whether it was a result of over pressurization or some other cause.
"We don't know if it was mechanical; we don't know if it was caused by over pressurization. We'll find that out as we work with plant and as we talk to the personnel," Edmondson said.
CF Industries' website says the plant can produce roughly 5 million tons of nitrogen for agricultural and industrial uses annually.
Just miles away Thursday, an explosion at a chemical plant in Geismar owned by Williams Cos. Inc. led to two deaths and injured dozens of others. Donaldsonville and Geismar are both in Ascension Parish and straddle the Mississippi River, between New Orleans and Baton Rouge.
Deerfield, Ill.-based CF Industries manufactures ammonia and other nitrogen fertilizers at its Donaldsonville plant. Edmondson said there was no ammonia at the plant at the time of the incident.
"There was no hazardous material at the site," Edmondson said.
Friday's deadly blast wasn't the first at the company's Donaldsonville plant. Three workers were killed and nine injured by an explosion and fire at the facility in May 2000.
Later that year, the Labor Department's Occupational Safety and Health Administration imposed a fine of nearly $150,000 against CF Industries. OSHA cited the company for 14 alleged safety and health violations, 12 of which were described by the agency as serious. The company didn't contest the citations and agreed to pay the penalties.