Firefighters said they were making good progress at keeping a 188,000-acre wildfire away from homes in the Illinois Valley after completing six miles of a backfire during the night. About 17,000 residents of the valley in southwestern Oregon had been warned that they could be told to evacuate with only 30 minutes' notice, although the immediate threat had lessened slightly, fire officials said. Nearly 1,000 people had left in the past week.