WINSTON-SALEM, N.C. — An uncontrolled fire at a fertilizer plant in North Carolina continued to burn Wednesday, forcing firefighters and thousands of evacuated residents to remain at least a mile (1.6 kilometers) away because there could be a large explosion.
Fire officials said they could not predict when the blaze might die down. And they didn't know how many people have actually obeyed the evacuation order.
"The fact of the matter is, at the beginning of this incident, there was enough ammonium nitrate on hand for this to be one of the worst explosions in U.S. history," Winston-Salem Fire Chief Trey Mayo said at an afternoon news conference that North Carolina Gov. Roy Cooper also attended.
"Our capacity to evacuate is limited," Mayo said. "And that's why we asked people to leave voluntarily."
The fire is at the Winston Weaver Company fertilizer plant on the north side of the 250,000-person city. The blaze began Monday night, shooting bright orange flames and thick plumes of smoke into the sky.
The fire quickly consumed the entire building, collapsing it. At least 90 firefighters had fought the fire for about 90 minutes Monday. But the risk of an explosion forced them to retreat. No injuries were reported.
Since then, drones and a helicopter have monitored the fire, and teams of firefighters have been on standby. A state police helicopter would fly over the scene Wednesday afternoon, Mayo said.
Officials initially thought the situation could end in 36 hours, maybe even two days. But Mayo abandoned making any predictions, saying that there was "too much product, too many unknowns."
An estimated 500 tons (454 metric tons) of combustible ammonium nitrate were housed at the plant and nearly another 100 tons (91 metric tons) of the fertilizer ingredient were in an adjacent rail car. That's more of the chemical than was present at a deadly blast at a 2013 Texas fertilizer plant blast that killed 15 people, Winston-Salem fire officials said.
"Ammonium nitrate has a history of being unpredictable. ... It's just sort of an enigma," Mayo said. "And we are giving it due regard because of its history."
The area that's been evacuated includes about 6,500 people in 2,500 homes, officials said. Wake Forest University, most of which lies just outside the evacuation zone, canceled classes and urged students in dormitories to stay indoors with windows closed.
Authorities warned of smoke and poor air quality in the city. Matthew Smith, a hazardous material expert with a regional state task force, said the gases released by the blaze are more of an irritant than something that could cause serious harm, barring an underlying lung condition.
Dr. Eric Sadler, a dentist whose office sits just outside the evacuation zone, said staff expressed reservations about coming to work over fears about the plant and the possibility of an explosion.
"A few of them were reluctant to come in today because of that," Sadler said Wednesday. "I did not do any arm-twisting. I told them it's their choice and I understood if they didn't want to come."
Sadler said his biggest concern is for people who live inside the 1-mile radius.
"I'm concerned about their homes, or people having homes to come back to if this blast actually does happen," he said. "That's a huge concern for me because that will be 6,000 people who will be homeless and displaced."
The fire also forced the evacuation of the headquarters of The Truth Network, a Christian broadcasting company that owns radio stations in North Carolina, Ohio, Utah and Virginia. It also syndicates radio programs across the U.S.
The network is running prerecorded broadcasts instead of its live programming because radio hosts cannot make it into the studios, according to Truth Network owner Stu Epperson Jr., who lives in Winston-Salem.
But Epperson, 51, stressed that he and his colleagues are far more concerned about the firefighters and people who live nearby. Many listeners are praying for them.
"We're just really praying for God's protection and for nothing to blow up," Epperson said. "Our prayers are going out to all the neighbors and residents and people at the fertilizer plant who have been displaced, and especially our first responders and firefighters."