About 300 workers have returned to Martinez Refining Co. following explosion fire over the weekend.

As Contra Costa County firefighters and company investigators sift through the damage, refinery workers have returned to their posts in an attempt to prevent further incidents, following numerous health advisories from the county department in recent days.

“I think some of the residents don’t understand that our workers are in there doing their best to prevent any further injuries and impacts to the surrounding community,” said Nick Plurkowski, president of United Steelworkers Local 5.

Employees were forced to evacuate Saturday afternoon when an explosion shot flames hundreds of feet into the air. Four refinery workers received minor injuries during the incident and were transported to local hospitals, according to Martinez Refining Co. spokesperson Brandon Matson.

Billowing, jet-black smoke over residential neighborhoods in Martinez, Pacheco and Clyde led to a shelter-in-place order Saturday evening from the county. The department lifted the shelter-in-place order around 9 p.m. Saturday night, but maintained a Level 2 public health advisory calling for sensitive populations to stay indoors.

The fire was mostly put out by 11 a.m. on Sunday, allowing refinery personnel to return to work in a limited capacity at designated safe areas of the refinery. Plurkowski said workers have been in the refinery since evacuations were lifted and are doing everything in their power to keep the affected communities and the refinery safe.

“It’s an oversimplification when I say this, but we’re scrambling around and seeing what we can do that’s still safe to do,” Plurkowski said. “The whole refinery is intertwined, and all the units affect the other units, so there’s stuff still going on.”

Gas prices ticked up slightly Monday, but one expert predicted a more significant spike due to the potential loss of the Martinez facility’s operations, which represent some 10% of the state’s refining capacity.

Martinez Refining Co. will be required to conduct an analysis to identify how the incident happened. Additionally, the refinery will be ordered to create and implement mitigation strategies to prevent future incidents, according to the county.

“We will continue to provide updates on our social media and have nothing further to add at this time,” Matson said.