Update, Nov. 25, 2016, 10:08 a.m.: The conditions of the four injured workers from Tuesday's fire at the ExxonMobil refinery have been upgraded, according to WAFB.

One worker's condition has been upgraded to fair, and the other three have been upgraded to serious condition.

Original story:

Four workers were injured in a fire at the ExxonMobil refinery Tuesday and taken to a Baton Rouge hospital's burn unit.  

The patients were all in critical condition, Meghan Parrish, a spokeswoman with Baton Rouge General Medical Center, said about two hours after the fire. 

Curt Monte, a spokesman for the Baton Rouge Fire Department, said EMS and fire trucks responded to the facility around 4 p.m. after a fire was reported inside the plant. It was extinguished by Exxon's internal fire team, he said. 

Mark Northcutt, the plant manager, said the team quickly put out the fire, which he described as occurring inside an "operating unit" in an isolated area. Neither Northcutt nor Monte said they knew the cause of the fire. 

"We really don't know at this point," said Northcutt, adding that the facility will start an investigation. 

(Video of Baton Rouge Fire Department Spokesman Curt Monte at the scene shortly after 5 p.m.)


Trouble seeing video? Click here. 

Both the Baton Rouge Fire Department and the Louisiana Department of Environmental Quality had teams at the plant, monitoring air quality at the perimeter of the facility to determine if anything was released in the fire. 

"Nothing has been picked up outside the facility," Monte said.

Northcutt said the four workers "received varying degrees" of burns. "Our thoughts and prayers are with them and ask for everyone else to be praying for them as well," he said.

The plant continued to operate after the fire, as Northcutt said the fire was confined to one area.

The fire occurred in an alkylation unit at the sprawling refinery, said DEQ spokesman Greg Langley. He said Tuesday evening he could not provide any additional details about the incident.

The huge refinery, which sits on 2,400 acres along the Mississippi River in north Baton Rouge, is the fourth-largest in the United States and processes more than 502,000 barrels of crude oil per day, according to the company's website.

The ExxonMobil refinery was the scene of a fatal explosion in December 1989, in which two people were killed and several others injured. There was also a fire at the facility in December of last year, but there were no injuries associated with that incident. 

A video (below) shows paramedics arriving on scene, but no visible smoke in the area.

* Editor's note: This article was changed after publication to correct the number of people killed in the 1989 explosion.

Advocate staff writer David Mitchell contributed to this report.