A team of federal bomb and explosives experts is hoping to finish tomorrow the task of removing aerial fireworks from the underground storage facility in Waikele where an explosion killed five workers April 8.

But determining exactly what caused the explosion might take a while longer, said Jordan Lowe, special agent in charge for the federal Bureau of Alcohol, Tobacco, Firearms and Explosives.

"This is going to be a very lengthy process," Lowe said. "Because of the tragedy that occurred, we want to make sure that we provide the most accurate information."

ATF is working with several other agencies, among them the independent U.S. Chemical Safety Board and the Honolulu Fire Department.

Three bomb technicians, three explosives specialists and a national response team leader joined up with two local ATF disposal specialists, including Lowe, on Monday to begin removing what is left in the cave, Lowe said.

The fireworks are being transported to a "secure, remote location" on the island where they are being disposed of through burning, he said.

The removal process needs to be completed before investigators can determine the cause and origin of the explosion, he said. "We can’t do that until we get the hazards out of the bunker. … Our primary focus right now is to mitigate the explosive hazards that right now are still in that magazine."

Until then Lowe is urging the public to stay out of the area. The concrete-enforced, 200-foot-deep cave is one of 300 built into the mountainside by the military during World War II as munition storage facilities. The tunnels are now operated by a private company for public business and retail storage.

The five men killed were employees of Donaldson Enterprises, a Wai­pio-based company with a federal contract to dispose of explosives and fireworks.

Donaldson has had a federal explosives manufacturing license, issued by the ATF, since 2002, Lowe said. The license allows the company to manufacture and dispose of explosives, including fireworks. He would not say where the activities took place or whether they took place in the facility where the explosion occurred.

Lowe declined to say specifically where the fireworks originated.

Lowe said yesterday that the fireworks were "seized as part of an ongoing investigation, but not by ATF." He declined to say which agency had confiscated the aerials or when they were seized.

Honolulu Fire Department officials said they issued Donaldson Enterprises a permit to store fireworks in the facility last year after inspecting the site.

Don Holmstrom, the U.S. Chemical Safety Board’s lead investigator in Waikele, said last week that his team was told the men were dismantling aerial fireworks when the explosion began.

ATF regulations bar processing and storing fireworks or other explosives in the same facility.

Lowe, however, would not say yesterday whether Donaldson had done that, and declined to give specifics about the ongoing investigation. "We’re looking into that," he said.

Generally speaking, fireworks confiscated by ATF are held by the agency "at a secure facility," Lowe said. If the fireworks are to be used for evidence in a criminal proceeding, what happens afterward may be determined by a judge or ATF.