A group of activists on Saturday marked the fifth anniversary of an explosion at the Exxon Mobil refinery in Torrance that injured four workers and prompted continuing concerns about the potential for an even more catastrophic incident and the release of toxic chemicals and fumes into local communities.

The explosion on Feb. 18, 2015, was described by federal regulators as “a serious near miss.”

The investigation of the Torrance explosion by the U.S. Chemical Safety Board revealed that a piece of equipment nearly crashed into a tank holding tens of thousands of pounds of modified hydrofluoric acid — a highly toxic chemical used to make high-octane gasoline.

When released, the chemical can form a deadly, ground-hugging cloud that, in the event of a major leak, could have caused “serious injury or death to many community members,” according to the agency.

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