Blasts have been heard at a chemical plant in Houston, Texas, which has been swamped with floodwater in the wake of Hurricane Harvey.
Officials warned on 30 August that they had no way of preventing a disaster at the Arkema plant in Crosby, after the facility lost power and its ability to refrigerate volatile chemical compounds that need to be kept cool.
It has also been confirmed that a police officer is being treated in hospital after being caught up in one of the explosions that released chemicals into the atmosphere.
The Federal Aviation Authority has issued a flight ban near to the plant with officials expecting it to explode.
Arkema CEO Rich Rowe said: "We have an unprecedented 6ft of water at the plant. We have lost primary power and two sources of emergency backup power.
"As a result, we have lost critical refrigeration of the materials on site that could now explode and cause a subsequent intense fire. The high water and lack of power leave us with no way to prevent it," he added.
Rowe said that all of the facility's personnel have been evacuated and that federal, state and local authorities have been contacted. "We are working very closely with them to manage this matter," he said. "They have ordered the surrounding community to be evacuated, too."
The plant was shut down late last week in anticipation of the storm but after 40in of rain, the area was flooded and back-up generators were also knocked out.
The site manufactures organic peroxides, compounds which are used for pharmaceuticals and construction materials, some of which can become explosive at high temperatures.
Around 33 people have died in the storm which first hit Texas on Friday 25 August.