Federal investigators are expected in south Louisiana over the weekend at the site of an explosion that killed one worker at a [CF Industries] chemical plant in Donaldsonville — the second such blast in the area in as many days...Lou Frey, vice president and general manager of the Donaldsonville Nitrogen Complex, said...“Our focus is on our number one priority — the health and safety of our employees and the community...We are deeply saddened by the loss of one of our employees.”... Three workers were killed and nine injured by an explosion and fire at the facility in May 2000.