An explosion has rocked a plywood manufacturing plant north of Houston, injuring seven workers and causing a fire that took hours to extinguish. The explosion occurred about 6:15 p.m. on April 26 at the Georgia-Pacific plant in Corrigan, Texas, a town about 90 miles north of Houston. Georgia-Pacific official Eric Abercrombie says four injured workers were flown to a Houston hospital. He says they suffered serious burns but that the injuries were not life-threatening. Three other injured employees were taken by ambulance to a hospital in nearby Lufkin. One of them has been released.