Updated

The U.S. Justice Department says it won't file criminal charges after investigating the April 2010 explosion that killed seven workers at the Tesoro refinery at Anacortes, Washington.

U.S. Attorney Jenny Durkan said Friday that the decision to close the case without charges was shared with victims' relatives earlier in the day.

Federal investigators and prosecutors examined whether environmental and worker safety laws and regulations had been violated.

The U.S. Chemical Safety Board released its final report on the blast in May. It blamed the facility's safety culture, industry standards, and state and federal oversight for the catastrophic rupture of a heat exchanger.

The board called for more conservative standards for the use of carbon steel and called on the state of Washington to adopt more rigorous safety management standards.