A state appeals judge has rejected a $2.4 million dollar fine for an oil company after a refinery explosion killed seven workers.

State officials imposed the fine on Texas company Tesoro in October 2010, over a blast in Anacortes, Washington, that occurred April that year. It was the largest workplace-safety fine in Washington state history, local NPR member station KUOW reports.

But late last week, Judge Mark Jaffe of the Washington State Board of Industrial Insurance Appeals overturned the fine, saying the state had not shown that the deadly explosion was Tesoro’s fault. The company had been appealing the fine for years — though it did pay millions of dollars to the families of the victims.

The local news website, GoSkagit.com, reports that Jaffe’s ruling must still be approved by the board.

The explosion occurred at the Tesoro’s Anacortes refinery when a heat exchanger ruptured. The rupture released extremely hot hydrogen and naphtha, which ignited. The ensuing explosion was so intense that many people felt a shock wave across the nearby Fidalgo Bay, and a huge fireball shot into the sky over the refinery, the Seattle Times reported at the time. (The outlet’s report was published before the final death toll.)

Seven workers — Daniel Aldridge, Matt Bowen, Matt Gumbel, Darrin Hoines, Lew Janz, Kathryn Powell and Donna Van Dreumel — died from injuries sustained in the blast, according to KUOW.

The state’s Department of Labor and Industries accused Tesoro of dozens of violations that contributed to the explosion, and these alleged violations led to officials handing down the $2.4 million fine.

“Our position has been that had Tesoro conducted the appropriate and required testing, they would have found the cracking that led to the rupture,” department spokesman Hector Castro told Reuters in 2011.

But Judge Jaffe wrote in his ruling on Thursday that the state was “unable to really articulate what Tesoro did or did not do to cause the explosion.”

The Washington Department of Labor and Industries, however, is not the only group that has blamed the company for the disaster.

The U.S. Chemical Safety Board said in 2011 that Tesoro inadequately maintained the heat exchanger that exploded, Reuters reported at the time.
The CSB released its final report on the catastrophe in 2014, citing a “substandard safety culture at Tesoro, which led to a complacent attitude toward flammable leaks and occasional fires over the year.”

The company has repeatedly asserted it was not at fault for the explosion and that its heat exchanger maintenance was in line with industry standards and regulations.

Tesoro spokesman Matt Gill told GoSkagit.com that the company supported Judge Jaffe’s decision.