Investigators from three agencies yesterday continued trying to learn what set off a powerful explosion Tuesday afternoon at PSC Industrial Outsourcing Co.'s facility in Campbell Industrial Park in Kalaeloa, killing a 23-year-old welder from Waipahu and hospitalizing three workers.

Capt. Terry Seelig, Honolulu Fire Department spokesman, said yesterday that department investigators were still sifting through evidence.

"The investigation is not finished yet," he said.

Seelig said a report on the findings should be available next week.

Meanwhile, Ryan Markham, spokesman for the state Department of Labor and Industrial Relations, said investigators with the agency's Occupational, Safety & Health division had been on the scene daily since the blast. He also indicated that his agency's final report would not be issued until next week.

But he did outline the labor department's priorities in the matter, based on information from the branch manager, and health and safety inspectors at the scene.

"Their first concern was whether there was any ongoing safety risks, and if the site's secure, and if there's any immediate or continued latent dangers involved — that sort of thing," he said.

Otherwise, he said, inspectors were there to find out what caused the accident, and whether a violation of state safety or health standards had occurred.

Honolulu Police Department spokesman Maj. Frank Fujii said that other than waiting for a few test results, police arson investigators have concluded that the explosion was an industrial accident.

"We're not pursuing anything criminal," said Fujii. "It's still classified as an unintended death. We're just awaiting the results of the autopsy and things like that. We need those before we can make a final determination."

Killed in the blast was Sean Norva, 23. He had been welding around a 9,500-gallon fuel oil tank when the explosion happened at around 1:30 p.m. He was hurled about 100 feet, striking a pickup truck in a nearby business property.

Preliminary autopsy findings listed cause of death as internal injuries "due to an industrial accident."