Two blasts were reported at Arkema chemical plant in Crosby near the flooded city of Houston in the United States on Thursday morning.
"At approximately 2 am CDT [07:00 GMT], we were notified by the Harris County Emergency Operations Center of two explosions and black smoke coming from the Arkema Inc plant in Crosby, Texas," the company said in a statement.
Hit by Hurricane Harvey, the plant had lost the ability to refrigerate chemical compounds. The company had earlier warned that an explosion cannot be prevented.
"Local officials had previously established an evacuation zone in an area 1.5 miles from our plant, based on their assessment of the situation. We want local residents to be aware that product is stored in multiple locations on the site, and a threat of additional explosion remains," a statement had warned.
"Please do not return to the area within the evacuation zone until local emergency response authorities announce it is safe to do so," it added.
Over 30 people have been killed in eastern Texas in the aftermath of the storm and heavy downpour is expected from Louisiana to Kentucky in the next three days. As oil companies closed down refineries, US energy supplies have also been affected.
"We'll be doing block-by-block, door-by-door search of streets... to make sure there are no people we've left behind," Richard Mann, the city's assistant fire chief, was quoted as saying by Houston Chronicle.
Before the storm made a landfall, the Arkema chemical plant, located 34 km from Houston, had shut down its production on last Friday.
"But 40in (102cm) of rainfall in the area flooded the site and cut off its power, the company said in a statement. Backup generators were also flooded. The facility manufactures organic peroxides, compounds that are used in everything from making pharmaceuticals to construction materials, which can become dangerous at higher temperatures," BBC reported.
"Any fire will probably resemble a large gasoline fire," CEO Richard Rowe had told Reuters before the reports of explosions. "The fire will be explosive and intense."
