Two explosions hit a Texas chemical plant flooded by Hurricane Harvey on Thursday, with a sheriff's deputy taken to hospital after inhaling fumes.
Arkema Inc, the French company that owns the plant, said further explosions of organic peroxides were possible, and urged people to stay away as the fire burns itself out.
Black smoke was billowing from the site, Harris County sheriff Ed Gonzalez told reporters at a televised news briefing.
A day earlier, the Federal Aviation Administration said it had temporarily barred flights from the area because of the risk of fire or explosion. Arkema evacuated remaining workers at the damaged plant on Tuesday, with Harris County ordering the evacuation of residents within a 2.4-kilometre radius.
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Assistant fire chief Bob Rayall said "a series of pops" at the scene had led to the fires. "We haven't had massive explosions," he added, emphasising that the fires had so far been contained.
Mr Rayall said three of the site's nine containers holding peroxide had lost refrigeration, and one had caught fire.
The plant, which lies about 40 kilometres north-east of Houston, lost power and its backup generators amid Hurricane Harvey's days-long deluge.
Arkema said it had no way to prevent fires because the plant is swamped by about 6 feet of water due to flooding from Harvey, which came ashore in Texas last week as a powerful Category 4 hurricane, knocking out power to the plant's cooling system.
The company said the Harris County Emergency Operations Centre notified it at about 2am local time of two explosions and black smoke coming from the plant in Crosby.
"Organic peroxides are extremely flammable and, as agreed with public officials, the best course of action is to let the fire burn itself out," Arkema said.
The peroxides are used to make plastic resins, polystyrene, paints and other products.
The sheriff's office said on Twitter that the deputy had been taken to hospital, while 14 others drove themselves there as a precaution. Eight have been released, and seven remain under observation.
The department said it believed the smoke was a "non-toxic irritant".
"Remain well clear of the area and follow directions of local officials," the National Weather Service said after the explosions.
Richard Rowe, chief executive officer of Arkema's North America unit, said on Wednesday that chemicals on the site would catch fire and explode if they were not properly cooled.
Arkema said it opted not to move chemicals before the storm but had made extensive preparations. A company spokeswoman did not immediately say when Arkema believes the fires will end.
Mr Rowe, however, said a fire would not pose any "long-term harm or impact".
The plant, which closed on Friday last week, has been without electric service since Sunday. It lost refrigeration when backup generators were flooded, and workers transferred products from warehouses into diesel-powered refrigerated containers.
The company said some refrigeration of backup containers has been compromised because of high-water levels and that it was monitoring temperature levels remotely.