Rescue workers continued to dig through debris on Thursday left by two tornadoes that swept through Massachusetts on Wednesday, killing at least four and injuring at least 200. About 39,000 people are still without power. Nineteen communities were hit by the tornadoes, which brought with them large hail and thunderstorms. The storms toppled power lines and sheared roofs off buildings. Governor Deval Patrick declared a state of emergency shortly after the storms struck yesterday, authorizing 1,000 National Guard troops for rescue and response operations.