Police said explosions were heard at about noon at the Mont Belvieu plant. The plant belongs to Enterprise Products, which is an energy company.
Enterprise said one contract worker is unaccounted for.
"We need to confirm if he was in there to begin with and then determine if anyone saw him leave or if anyone saw him not leave," Enterprise spokesperson Rick Rainey said.
There were no reports of injuries or evacuations, but a nearby school district kept students inside during the fire.
According to Enterprise, an employee in the control room had an inkling something was wrong and began shutting down lines shortly before the explosion. They don't yet know the cause, though they suspect that a rupture in the pipeline caused the blast.