All other personnel were accounted for, Exxon said, adding that its emergency response crews were still working to extinguish the blaze.
The Baytown plant houses a chemical plant, an olefins plant, and the country’s fourth biggest oil refinery, with capacity to process 560,500 barrels per day of crude.
Three people were evacuated by Lifeflight rescue helicopter and a fourth person was taken by ambulance, Harris County Sheriff Ed Gonzalez said on Twitter.
Initial reports indicated there had been some type of explosion at the plant, but there were no reports to evacuate or shelter-in-place at the moment, the sheriff added.
Social media users said on Twitter that a blast shook buildings in the area.
The Baytown olefins facility, which began operations in 1979, is one of the largest ethylene plants in the world, according to the company’s website.
Production was reduced across the Baytown refining and petrochemical complex in August 2019 because of a fire in a propylene recovery unit at the olefins plant.
As many as 37 workers were injured in another fire at the olefins facility in July 2019.
By Arpan Varghese