Fears are growing that a Texas chemical plant flooded by Tropical Storm Harvey will soon explode and cause an intense fire.
The deluge from Harvey and a lack of power led the boss of the Arkema plant near Houston to warn it could combust.
It comes as flood waters begin to recede across parts of the Texas city.
Five days of torrential rain has submerged Houston, America’s fourth-largest city, while three flood defenses – one of which is designed to withstand a “1,000-year flood” – have overflown.
Homes within a 1.5-mile radius of the Arkema plant in Crosby, which is 25 miles northeast of Houston, have been evacuated.
The work site was shut before Harvey made landfall last week, while all remaining staff were sent home on Tuesday.
An explosion and intense fire are expected as the plant is surrounded by six feet of water, meaning chemical compounds – which must be stored at low temperatures – will warm up.
Meanwhile, US President Donald Trump has promised billions of pounds in aid to help Texas rebuild.
It is believed that the US has $2.3 billion in disaster funds.
Harvey was downgraded to a tropical depression on Thursday, but experts expect more catastrophic flooding.
The death toll from Harvey has been raised to 20, but a further 17 deaths are being investigated as potentially Harvey-related.
Police said officers had found a submerged van in which a Houston family of six was killed as they tried to escape the flood waters.
The two grandparents and four children, aged six to 16, died after their van sank in Houston.
Around 24,000 members of the National Guard are being deployed in the state to help with disaster relief.
Houston’s mayor, Sylvester Turner, imposed a night-time curfew between 10pm and 5am in a bid to prevent looting and protect public safety.