A fire broke out Monday night at the Winston Weaver Company fertilizer plant in Winston-Salem, North Carolina. It is still unclear what caused the blaze. The fire was still active Tuesday morning according to Winston​-Salem Fire Department Battalion Chief Patrick Grubbs said during at a news conference early Tuesday morning.

Grubbs said, “We fought the fire for two hours before the blaze began affecting a rail car. Once the rail car was involved, it became an explosive hazard, with the potential for an explosion of ammonium nitrate.” Grubbs added, “That development forced at least 90 firefighters involved to pull back.”  

The Associated Press (AP) reported the City’s fire department said it could not provide enough water to be “reasonably certain” there wouldn’t be an explosion. Ammonium nitrate is chemical compound used as a source of nitrogen for fertilizer. It is also used to create explosives for mining, however. 

Winston-Salem Mayor Alan Joines told reporters Tuesday morning every household within a one-mile radius of theWinston Weaver Company plant was asked to evacuate as authorities said there was still a chance for an explosion.Over 6,000 residents have been asked to evacuate their homes. “We’re asking everyone to stay out of this area,” officials said.

According to the city’s Twitter page, 2,497 households, almost 6,500 residents, are in the evacuation radius. 

Also, Wake Forest University, though mostly outside of the evacuation zone, decided to cancel classes on Tuesday, as one of the university’s buildings and many students living off-campus were in the zone, according to the AP.

WGHP reported facilities in the evacuation radius, such as North Hills Elementary School and Forsyth Correctional Facility, have been affected. City officials told the local news outlet the prison inmates have been removed while the school told parents it would implement remote learning Tuesday with teachers calling students to check in on them.

Mayor Joines added, “Personally and on behalf of all our citizens, I thank Fire Chief Trey Mayo and his team for keeping things under control and taking actions needed to protect our citizens.”

This is a developing story and will be updated as information is made available.