Officials at the Arkema plant in Crosby, northeast of Houston, had left volatile chemicals in nine truck-sized containers after the storm cut power used to cool the organic peroxides used to make plastics and other materials.
Local TV footage this evening showed a fresh blaze and thick black smoke.
An employee at the plant confirmed to AFP: "It's the reaction we were expecting to happen.
The first of the nine containers caught fire and burned for nine hours overnight Wednesday into Thursday.
It forced the evacuation of hundreds of residents within 2.4 kilometers of the plant.