The Casino Fire near Oglala, South Dakota, has burned 12,636 acres since it began Tuesday afternoon.
The fire started near the Prairie Wind Casino, and its cause is still unknown.
Oglala Sioux Tribe Emergency Management says winds Thursday created spot fires that turned into another large wind-driven blaze.
Fire crews from the Bureau of Indian Affairs and other federal, state and local groups are still trying to create containment lines and put out hot spots.
There are three fire suppression teams, 14 wildland fire engines, two bulldozers and three water tenders on the scene. OST Emergency Management says crews are working 24 hours a day to monitor the fire and respond to any flare-ups that may occur.
The fire was 51 percent contained as of Thursday.
