“Our fire teams are working to extinguish the fire. We are conducting personnel accounting,” Exxon said.

Harris County sheriff Ed Gonzalez said on Twitter that three people were evacuated by Lifeflight rescue helicopter and a fourth person was taken by ambulance.

Initial reports indicated there had been some type of explosion at the plant, he said.

There were no reports to evacuate or shelter-in-place at the moment, the sheriff added.

The Baytown police department said the plant unit affected in the incident processed material with gasoline components.

Sources familiar with the Baytown complex operations said the fire was in the Baytown olefins Plant but said no more details were immediately available.

Social media users said on Twitter that a blast shook buildings in the area.