U.S. Army fire officials were investigating the cause of a brush fire in Wahiawa that prompted school officials to take precautions from ill-effects of the smoke on Friday.

Iliahi Elementary School principal Dale Tanouye said students and teachers were asked to stay in their classrooms and to shut their windows and place towels on the bottom of door, until air quality returned to levels in which outside activities could resume.

The school is located along California Avenue, about a mile mauka of Leilehua High School.

The fire, burning about five acres in the Army’s east range, started at about 11:30 a.m. and was 90 percent contained by 2:15 p.m. , Honolulu Fire Capt. Terry Seelig said.

Seelig said city firefighters worked with firefighters from the Army and federal government to contain the blaze.