A stubborn brushfire on a hillside behind Kailua High School burned about 50 acres and was 80 percent contained as of 5 p.m., Honolulu fire Capt. Terry Seelig said.

The fire burned a hillside bordered by Kailua High School, Hamakua Drive and Akiohala Street, which leads to the back end of the school.

It came up to the fence line of the high school and within 20 feet of some of the school’s buildings, Seelig said. On the other end of the fire, flames came within 100 yards of the closest home, Seelig said.

The fire was reported at 12:20 p.m. Some 70 firefighters from 12 companies responded, along with two helicopters and two water tankers, Seelig said.

Fire investigators are likely to return to the scene tomorrow to determine the cause of the blaze, Seelig said.