CROCKETT (KRON) – Cal/OSHA has shut down NuStar until the company can prove it can operate safely again.

The decision to cease all operations at the NuStar Energy storage facility comes after Tuesday’s fire and explosion that burned two tanks containing thousands of gallons of fuel and prompted an hours-long closure of nearby freeways.

The explosion also caused concerns regarding air quality issues, with the main issue being that hazardous particles may be spewing into nearby areas from the fire.

Investigators have also served a search warrant on the facility.

The cause of the fire and explosion remains under investigation, and officials say it’s still too early to tell if it was triggered by the 4.5-earthquake that hit late Monday in Pleasant Hill.

Randy Sawyer, Contra Costa County’s chief environmental health and hazardous materials officer, said that Tuesday’s earthquake caused malfunctions at two nearby oil refineries operated by Shell and Marathon oil.

The Bay Area Air Quality Management District is also part of the investigation.

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