A chemical plant near the flooded city of Houston is expected to explode or catch fire in the coming days.
During heavy rainfall from Hurricane Harvey, the Arkema plant at Crosby lost refrigeration of chemical compounds which need to be kept cool, and there is no way to prevent a possible fire, the company said.
At least 33 people have been killed in the aftermath of the storm.
US energy supplies have also been hit, as oil companies shut down pipelines.
The US National Weather Service downgraded the former hurricane to a tropical depression but has forecast continuing heavy rainfall over eastern Texas and western Louisiana.
An additional 10,000 members of the National Guard were said to be on their way to Texas to join the rescue efforts, adding to the 14,000 already deployed.
Harvey was the most powerful hurricane to hit Texas in more than 50 years when it first made landfall at Corpus Christi, 220 miles south-west of Houston, late on Friday.
At a press conference Wednesday, Texas Governor Greg Abbott said the state could need more than $125bn (£97bn) from the federal government to help its recovery.
And he warned "the worst is not yet over", as flooding was expected to continue for several days.
Meanwhile, the tropical depression is now moving north-north-east, the US National Weather Service said.
Heavy rainfall is expected from Louisiana to Kentucky over the next three days, and flood warnings remain in effect for south-east Texas and parts of south-west Louisiana.