WINSTON-SALEM, N.C.—An uncontrolled fire raging at a North Carolina fertilizer plant forced the evacuations of thousands of people as firefighters warned early Tuesday that chemicals at the site could cause 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 Weaver Fertilizer Plant on the northside of Winston-Salem, where the fire started Monday night. Bright orange flames could be seen shooting into the sky along with thick plumes of smoke as lights from firetrucks and other first responder vehicles surrounded the fully engulfed building. The evacuation area included about 6,500 people in 2,500 homes, the Winston-Salem Fire Department said. “We want to make sure that right now we’re evacuating everybody in this one-mile radius,” Winston-Salem Battalion Chief Patrick Grubbs told reporters early Tuesday. “There is still a potential for explosion.” Firefighters had pulled back from the scene …