CHARLOTTE, N.C. — The city of Winston-Salem is working to evacuate 6,500 people as fears grow a smoldering fertilizer plant might explode near thousands of homes. Fire trucks patrolled the mandatory evacuation area throughout early Tuesday morning, blowing their horns and blasting a warning for people to evacuate as quickly as possible. The mass exodus is due to a potentially explosive fire at the Weaver Fertilizer Company in north Winston-Salem. Just under 2,500 homes are within a mile of the plant, which stores tons of explosive materials as part of its products, the city said in a tweet. Re…