Local authorities in Texas issued an immediate shelter-in-place order on Monday (March 23) following an explosion at Valero’s Port Arthur refinery, as emergency crews responded to an active fire at the facility. There were reports of a boom and smoke was seen rising from the plant about 90 miles (145 kilometers) east of Houston, ABC TV affiliate 12News reported.

"To ensure the safety of all residents in the vicinity and in light of the recent explosion at the Valero refinery, an immediate shelter in place is ordered," Port Arthur emergency management officials said in a public alert, applying the directive to a wide area surrounding the site.

Valero confirmed that a fire had broken out within one of the refinery’s units but stated that all personnel had been accounted for. "Currently there is a fire in a unit at Valero's Port Arthur, Texas refinery. All personnel have been accounted for," the company said, adding that worker safety remains a “top priority.”

Footage from local media showed large flames and thick black smoke rising from the refinery, while residents reported a loud explosion that shook nearby homes.

A fire broke out at a diesel hydrotreater, with the unit suffering severe damage, according to people familiar with the incident. The fire was near the plant’s fluid catalytic cracker, and part of the refinery has been shut down, according to the people, who said a decision hasn’t yet been made whether to shut the entire plant.

A few minor injuries were reported, according to people familiar. A Valero spokesperson said all personnel have been accounted for. Local officials have shut two nearby state highways as a precaution, the spokesperson said.

There were reports of a boom and smoke was seen rising from the plant about 90 miles (145 kilometers) east of Houston, ABC TV affiliate 12News reported.

The refinery can process 435,000 barrels of heavy sour crude a day, according to the company’s website.

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The Port Arthur refinery, located approximately 90 miles east of Houston, is one of the largest in the United States, processing around 435,000 barrels of crude oil per day into refined products including gasoline, diesel and jet fuel.

Texas state Repsrentative Christian Manuel said in a post on social media that the Texas Commission on Environmental Quality had arrived at the refinery with air monitoring equipment and was working with local and state partners.

He told nearby residents to stay inside.

“Please limit outdoor activity, keep windows and doors closed, and follow guidance from local officials,” he said.

No one was injured in the explosion at the Valero refinery in Port Arthur, about 90 miles (145 kilometers) east of Houston, Mayor Charlotte M. Moses said. She urged residents in parts of the west side of the city to stay put, saying fire fighters had arrived.

“There's been an explosion, yes, but we're OK; everybody's OK," she said. "They're trying to put the fire out as quickly as possible.”