A fire that has scorched about 400 acres of brush behind Kalaheo High School and the neighboring Kalaheo Hillside community was intentionally set, Honolulu Fire Department investigators have determined.

The fire appears to have started in an area of vegetation about 100 yards behind Kailua Assembly of God Church, said Capt. Terry Seelig, Honolulu Fire Department spokesman.

Physical evidence is pointing to several points of origin in the vicinity of two makeshift forts or clubhouses, Seelig said. “They didn’t have roofs, they didn’t have walls, just a framework for putting up a tent.”

Seelig said they did not appear to be homeless encampments, but more like gathering places. There were trails leading to and from the structures.

The fire department declared the fire a little over 90 percent contained at 1:30 p.m. Firefighters continue to monitor the situation.

The Kaneohe-bound lanes of the H-3 Freeway between Mokapu Boulevard and Marine Corps Base Hawaii offramp were reopened about 1:27 p.m., about four hours after they were closed to allow firefighters to battle the blaze.

Smoke and low light in the early morning hours created dangerous conditions for firefighters monitoring the fire from the freeway, Seelig said.

On Tuesday, strong winds blew the fire up the flank of the hill away from homes but toward Kaneohe and H-3 where firefighters were waiting. Rough and steep terrain, as well as the distance hoses would have needed to extend, made it difficult for the firefighters to reach too far up the Kaneohe side, Seelig said.

The fire was mostly contained by about 10 p.m. but firefighters kept watch from the Kaneohe side through the night, monitoring for hot spots.

The fire came within 25 to 50 yards of Kalaheo Hillside homes, as well as the Kalaheo High campus on Tuesday afternoon. No one was evacuated, but police warned residents to pack up and be prepared to leave.