The Bureau of Land Management said a range fire near Arimo and Downey should be fully contained by 8 p.m. Thursday.
The Cambridge Fire was reported around 2:45 pm Wednesday. It is burning 7 miles southeast of Arimo, or 4 miles east of Virginia, near Cambridge Road.
After more accurate GPS mapping the fire is estimated to be 388 acres.
Lynn Ballard with the Eastern Idaho Interagency Fire Center said the cause of the fire is thought to be from a lightning strike earlier this week.
The fire is burning in grass, brush and junipers.