One large group of fires was known as the Snake River Complex. These fires were in the southern section of the park, in the headwaters region of the Yellowstone and Snake Rivers. The largest fire in the group was the Shoshone fire which was started by lightning on June 23. The prescribed natural burn policy was still in effect, and at first no efforts were made to suppress this fire. It smoldered with little movement for several weeks, then rapidly started expanding towards the northeast on July 20.