A makeshift shrine near the accident site.

After being forced to wait several days for a storage bunker to cool enough to enter, federal investigators have begun investigating a fatal fireworks explosion near Honolulu, Hawaii.

The blast, which killed five workers, occurred on Friday in a bunker leased by Donaldson Enterprises, Inc., a company contracted by the federal government to destroy illegal fireworks that had been confiscated.

A team of investigators from the U.S. Chemical Safety Board (CSB) led by Investigator-in-Charge Don Holstrom arrived in Honolulu on Sunday and began interviewing eyewitnesses and documenting site conditions.

After agents from the Bureau of Alcohol, Tobacco and Firearms found additional explosives inside the bunker, it was deemed to dangerous for investigators to enter until Tuesday.

The CSB conducts root-cause investigations of chemical accidents at fixed industrial facilities, according to a statement by the board. Root causes include deficiencies in safety management systems and critical factors that would have prevented the accident had they not occurred. Other accident causes may involve equipment failures, human errors, unforeseen chemical reactions or other hazards. The CSB does not issue fines or citations, but does make recommendations to plants, regulatory agencies such as the Occupational Safety and Health Administration (OSHA) and the Environmental Protection Agency (EPA), industry organizations, and labor groups. In accordance with its Congressional mandate, the CSB is independent of all other government agencies so that its investigations might, where appropriate, review the effectiveness of regulations and regulatory enforcement by regulators.

The CSB investigative staff includes chemical and mechanical engineers, industrial safety experts, and other specialists with experience in the private and public sectors. Many investigators have years of chemical industry experience. The CSB team is likely to conduct detailed interviews of witnesses such as plant employees, managers, and neighbors, and obtain chemical samples from the accident site that may be sent to independent laboratories for testing. Company safety records, inventories, and operating procedures will also be examined in an effort to determine the cause of the accident.