WINSTON-SALEM, N.C. (AP) — WATCH: 3:15 p.m. press conference update:
An uncontrolled fire at a fertilizer plant in North Carolina forced thousands of people to evacuate as firefighters stood back Tuesday because of the danger of a large explosion.
Authorities drove through neighborhoods and knocked on doors asking residents to leave within a one-mile radius (1.6 km) of the Winston Weaver Company fertilizer plant on the north side of Winston-Salem, where the fire started Monday night. Overnight, bright orange flames and thick plumes of smoke could be seen shooting into the sky. No injuries were reported.
The city's fire chief said the fire had been "relatively static" overnight, but with 600 tons of combustible ammonium nitrate stored at the site, the risk of an explosion would remain through Wednesday.
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"We've got about a 36-hour window where that explosion potential exists" Winston-Salem Fire Chief Trey Mayo told reporters.
Wake Forest University, most of which lies just outside the evacuation zone, canceled classes and urged students living in dormitories to stay indoors and keep windows closed.
The evacuation area included about 6,500 people in 2,500 homes, the Winston-Salem Fire Department said.
At least 90 firefighters fought the fire for about 90 minutes after it was discovered at a loading dock around 7 p.m. Monday, but the risk of an explosion forced them to retreat, Mayo said. The fire quickly consumed the entire building and caused it to collapse. An unmanned fire truck was left behind to continue pumping water onto part of the site.
Drones and a helicopter monitored the fire from above, and teams of firefighters were on standby, but they had to let the fire burn for now, the chief said.
Mayo told reporters Tuesday morning that an estimated 500 tons of ammonium nitrate were housed at the plant and another 100 tons of the fertilizer ingredient were in an adjacent rail car. He said that is more of the chemical than was present at a deadly blast at a 2013 Texas fertilizer plant blast that killed 15 people, most of them emergency personnel.
"So if that doesn't convey the gravity of the situation and how serious folks need to take it, I don't know how else to verbalize that," he said.
Mayo said the chemical generally needs to be in a confined space to explode, so the risk will depend on whether the material is stacked deep enough for the top layers to put enough pressure on the bottom layers.
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Authorities warned of smoke and poor air quality in the city of about 250,000. Matthew Smith, a hazardous material expert with a regional state task force, said the gases released by the blaze are considered more of an irritant than something that could seriously harm someone, unless they have an underlying lung condition.
The Forsyth Correctional Center, a minimum security prison with the capacity for about 250 inmates, also is in the evacuation area.
Winston-Salem officials said a shelter has been set up at the Winston-Salem Fairgrounds.
A representative from the Winston Weaver Company didn't immediately respond to an email seeking comment.
Richard Van Erp, who lives blocks from the fertilizer plant, said late Tuesday morning that so much smoke was billowing into his apartment complex's parking lot that he couldn't see the cars at times. He said it appeared many residents hadn't yet evacuated.
Van Erp, who doesn't have a car, said he had called a non-emergency police number to ask for a ride to a shelter and was waiting to be picked up.
"It takes a lot to spook me, and I will say I'm pretty shaken right now," he said. "They said that, more than likely if it blows, the evacuated area will be leveled completely. I'm not even a quarter of a mile away. I'm done if I don't get out of here."
___ Finley reported from Norfolk, Virginia.