SEATTLE -- A report released late Wednesday night into the 2010 explosion at an oil refinery in Anacortes concludes safety culture deficencies by the refinery operator and state officials contributed to the accident.

Seven people died in the explosion and fire in the early morning hours of April 2, 2010 at the Tesoro facility in Anacortes.

The investigation by the U.S. Chemical Safety Board chronicles the deadliest oil refinery accident in the nation since 2005.

Heat exchangers, located in the part of the plant which turns crude oil into gasoline, had been leaking for years and directly led to the fire, federal investigators said.

According to the report, the exchangers were being turned back on after being cleaned, a task made more dangerous by the weak quality of the equipment.

The CSB also released animation that recreated the blast and fire. The five-minute video illustrates how the heat exchanger was damaged and weakened over the years.

Watch the animation:

All of the fatally injured employees lacked fire retardant safety equipment, and Tesoro management accepted the leaking as part of the process, even though federal officials said it could have been avoided.

Tesoro was already fined more than $2 million by Washington Labor and Industries, but federal investigators found issues with state officials as well. In addition, the families of the killed workers settled with Tesoro and Shell Oil for $39 million, according the families' lawyer.

The Chemical Safety Board reported signifigant gaps in the competency of state investigators, citing frequent swaps with Tesoro over citations and fines in exchange for increased audits by the company. Those audits, the CSBwrote, are inadequate.

The results have some family members scratching their heads.

You can't stop wondering how could this have been prevented, says Hershel Janz, father of Lew Janz who was killed in the blast.

We have better regulations on cars and buildings all the time. Why can't we have better oversight with the refineries.

The CSB also uncovered concerns raised by the United Steelworkers Union prior to the accident with the heat exchangers.

Wednesday, the union hosted a private meeting with family members of the deceased to discuss the report, and a public eventThursday night where the CSBwill present its findings to the community.

There are unanswered questions for me, said Cory Bowen, who works at the Tesoro plant and lost his brother in the explosion, We as humans aren't taught how to grieve. The grieving process for my family has been very difficult.

Tesoro released the following statement in response to the report:

Tesoro deeply regrets the incident of that day. Our thoughts and prayers remain with the families and friends of our seven co-workers who lost their lives. The Company recognizes the public receipt of the CSB's draft investigation report and acknowledges the efforts of CSB investigation teams, despite the significant and successive turnover in the agency's assigned personnel over the years. We respectfully disagree with several findings in the draft report and, most importantly, take exception to CSB's inaccurate depiction of our process safety culture. However, despite any disagreements regarding the draft report, Tesoro anticipates discussing the CSB's recommendations with the agency once the report is finalized and will consider them in light of the steps we have taken and are continuing to take to improve the safety of our facilities.

Tesoro Anacortes 2014-Jan-27 by KING 5 News

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