AUSTIN, Texas — Wildfires fueled by dry conditions and gusting winds burned in a few Southern states Thursday, forcing evacuations in Texas and prompting Florida officials to close part of a major highway with spring break in high gear. A wildfire in Sam Houston National Forest near Houston prompted the evacuation of about 900 homes and closed schools. The National Weather Service issued elevated fire warnings around the nation’s fourth-largest city. The fire burned about 3.7 square miles (9.6 square kilometers) and was only about 20% contained Thursday afternoon as firefighters used water-carrying helicopters to douse hot spots and bulldozers to dig containment lines, the Texas A&M Forest Service said. Investigators believed the fire was started Wednesday by what was supposed to be a controlled burn on private property, said Josh Mizrany, assistant chief law enforcement officer with the Texas A&M Forest Service.