During September 7–10, firefighter mopped up along existing fire line while fuels within the fire perimeter continued burned in some areas. On the southwest side, the fire kept on burning slowly down slope through the Three Sisters Wilderness Area, occasionally torching pockets of taller trees."Milli Fire News Release", InciWeb Incident Information System, Deschutes National Forest, United States Forest Service, Bend, Oregon, 7 September 2017. On 8 September, thunderstorms passed through the region, dropping a light rain over much of the fire area. The moisture reduced fires activity and aided humidity recovery."Milli Fire News Release", InciWeb Incident Information System, Deschutes National Forest, United States Forest Service, Bend, Oregon, 8 September 2017. During this period, the number of firefighters on station was steadily reduced to 59 on September 10. On that date, the Forest Service estimated the Milli Fire covered with containment remaining at 60 percent. The total cost of fighting the fire was estimated at $15 million."Milli Fire News Release", InciWeb Incident Information System, Deschutes National Forest, United States Forest Service, Bend, Oregon, 9 September 2017."Milli Fire News Release", InciWeb Incident Information System, Deschutes National Forest, United States Forest Service, Bend, Oregon, 10 September 2017. Between September 11 and September 14, the fire continued to burning slowly down slope through the Three Sisters Wilderness toward lava beds, which create a natural fire break because there was no fuel to burn in the lava fields. During this period, fire crews patrolled the existing fire lines and finished mopping up hot spots. Forest Service and Oregon Department of Transportation crews also removed hazardous trees from the Route 242 corridor and repaired culverts along the roadway."Milli Fire News Release—Update Sept. 11–14", InciWeb Incident Information System, Deschutes National Forest, United States Forest Service, Bend, Oregon, 11 September 2017."Milli Fire Begins to Wind Down in Sisters", Nugget News, Sisters, Oregon, 12 September 2017.
