An illegal, professional-grade aerial firework set off the Fourth of July wild fire that burned 200 acres of brush in Kalama Valley, threatened $50 million worth of homes and forced the evacuation of dozens of residents, Honolulu fire officials said this afternoon.

Firefighters were still trying to extinguish the fire above Kalama Valley on Kamehame Ridge this afternoon, although residents were allowed to return to their homes.

A Red Cross shelter at Koko Head District Park closed this morning after housing about 15 evacuees overnight.

The fire was about 85 percent contained as the Honolulu Fire Department held its annual news conference to report on Fourth of July fireworks-related fires at 1 p.m. today.

A total of 12 wild fires and four rubbish fires on Oahu were likely ignited by fireworks on the Fourth of July, Honolulu fire Capt. Terry Seelig said.

The department normally responds to eight fire calls in a 24-hour period, but handled 51 between 12:01 a.m.Saturday and midnight Sunday — including a stubborn wildifre between Kalaeloa and Ko Olina — that stretched the fire department’s firefighters and equipment, Seelig said.

The 300-acre Ko Olina fire was initially reported at 9:45 p.m. on Saturday in a hard-to-reach area full of gulches and ravines, Seelig said.

That fire came within a few hundred yards of townhomes at “The Fairways” complex in Ko Olina. Crews worked to protect utility poles and a pumping station as the fire spread in several directions, Seelig said.

The cause of the Ko Olina fire was still undetermined, Seelig said.

From the fire department’s perspective, the evening of the Fourth of July was shaping up quietly, with only the pesky Ko Olina fire continuing to flare up with hot spots.

But then residents along Kamehame Ridge reported that a huge percussive — and illegal — aerial firework had landed in the brush along Kealahou Street at 9:30 p.m., half an hour past Oahu’s time limit to set off legal fireworks.

The fire quickly spread along the ridge and up the valley, burning 200 acres of brush and threatening dozens of homes in the back of the valley worth about $50 million, Seelig said.

“Walls of flames 20 to 30 feet tall” came within 75 feet of homes with shake roofs, Seelig said. 

“Imagine looking out your back door and seeing the ridge on fire,” he said.

More than 12 fire companies and 50 firefighters fought the blaze. The wild fire consumed more than 200 acres and firefighters and the department’s helicopter returned to the scene this morning to mop up “hot spots,” he said.

At one point the fire endangered more than 10 campers who were spending the night at the Hawaii Army National Guard’s old Nike missile site.

Seelig said the hikers decided to leave the area using a trail on the Hawaii Kai side of the ridge and the fire department’s helicopter used its searchlight to mark the trail.

As the fire raced up the valley, at least 10 unrelated fire calls poured into HFD from 9:30 p.m. to 10 p.m., including two other brush fires and a report of building fire in Waianae that turned out to be merely plumes of fireworks-related smoke, Seelig said.

With so much activity tying up 33 percent of the fire department’s companies, fire officials went to “Level 2 staffing,” which meant prioritizing calls.

“We didn’t have the resources to send to them immediately, like we normally do,” Seelig said.

Star-Advertiser Reporter Gregg Kakesako contributed to this story.