Fire Marshal Charles Britt said the Mountaire plant was evacuated about 10 a.m., WRAL-TV in Raleigh reported. A state highway near the plant in Lumber Bridge near Fayetteville was also closed for much of the day.
In a preliminary finding, fire investigators blamed a broken high-pressure hose carrying ammonia for the blast.
The dead man was identified as Clifton Swain of Fayetteville. Sheriff Kevin Sealey did not release the names of the injured, including one taken by helicopter to UNC Hospitals in Durham while the others were transported to Cape Fear Valley Regional Hospital.
Mountaire Valley Farms Inc. employs about 2,500 people at the plant. But only 30 or 40 were at work Saturday morning.