Officials are now expecting to wrap up the removal of hazards from an underground storage bunker in Waikele where five men were killed April 8 in a fireworks explosion.

Only then will investigators with the federal Bureau of Alcohol, Tobacco, Firearms and Explosives; the Hono­lulu Fire Department; and other agencies begin to explore the cave in earnest in an attempt to discover what caused the tragedy, ATF and HFD officials said yesterday.

The five men were employed by Wai­pio-based Donaldson Enterprises, which has a federal subcontract to dispose of contraband aerial fireworks and had a license to store fireworks in the 200-foot storage facility. The storage unit is one of 300 constructed into the mountain at Waikele Gulch by the military during World War II to store explosives and now leased out to businesses and individuals.

The agencies released to media yesterday video footage and still photos of the contraband aerial fireworks from the cave being detonated by federal officials. The visuals displayed the explosive power of the fireworks, with a fiery ball rising more than 100 feet into the air.

A team of about seven federal bomb and explosives specialists began removal of the explosives on Monday and had expected to finish yesterday.

"It’s taking a little bit longer than we anticipated," ATF spokes­man Joe Green said, noting the complexity of the process and potential for danger.

"We try to be very methodical on how we do disposals because it’s a safety issue," said Jordan Lowe, an explosives specialist and resident agent in charge for ATF’s Hawaii office.

There was little new information released about what has been found so far.

Investigators declined to disclose the quantity of aerial fireworks found in the storage area.

Lowe said they were "not consumer variety."

No military explosives were found there, he said.

Where the contraband came from is also still a mystery, as is what the workers were doing when the explosion occurred.

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

USAspending.gov, a federally run website, states that Donaldson Association was awarded a $150,000 subcontract for "destruction services" on Nov. 10. The subcontract is under a $25.9 million contract awarded in September by the U.S. Department of the Treasury to VSE Corp., an Alexandria, Va.-based company, under the description "property management and disposition services."

An investigator with the U.S. Chemical Safety Board said last week that the tunnel was being used not just for storage, but for preparation for demolition at another, unidentified location. Federal rules found on the ATF website bar anyone with an explosives or fireworks license from process­ing such materials where they are stored.

But federal and city officials again declined yesterday to discuss that point with reporters, calling it part of the ongoing investigation.

Honolulu fire Capt. Terry Seelig said the situation posed "without a doubt … one of the most difficult investigations that the HFD has done."

There’s no guarantee that investigators will be able to come to a "definitive cause" for the explosion, Seelig said, "but we can devote considerable resources, as we owe the families of those who were fatally injured our best efforts," he added.

"This is a significant event," Lowe said.