The death toll from Storm Harvey has risen to at least 18 – as it became the heaviest tropical downpour in US history.
Five days of torrential rain has submerged Houston, America’s fourth-largest city and three major flood defences – one of which is designed to withstand a ‘1,000-year flood’ – have begun to overflow.
Houston’s mayor, Sylvester Turner, imposed a night-time curfew between 10pm and 5am in a bid to prevent looting and protect public safety.
Mr Turner said he had asked the US Government to provide supplies, cots and food.
More than 17,000 people have sought refuge in Texas shelters and the American Red Cross said this figure was likely to increase.
A family of six died trying to escape the Texas floodwater are among the dead.
The two grandparents and four children, aged six to 16, died after their van sank in Houston.
Authorities confirmed Houston police officer Sergeant Steve Perez, 60, drowned in his patrol car after he became trapped in high water while driving to work.
A woman was killed when heavy rain dislodged a large tree on to her trailer home in the small town of Porter and there are other reports of people missing or presumed dead.
A hotel in the city said one of its employees disappeared while helping about 100 guests and workers evacuate the building amid rising floodwaters.
Houston police chief Art Acevedo said: “I’m really worried about how many bodies we’re going to find.
“We know in these kind of events that, sadly, the death toll goes up, historically.”
Rescuers are continuing to pluck people from inundated neighbourhoods, with the National Guard carrying out or assisting in 3,500 rescues.
The Coast Guard said it was taking more than 1,000 calls per hour.
Donald Trump is in Texas for briefings on the government’s work to help the state recover from Harvey, which has been downgraded from a hurricane to a tropical storm.
Addressing crowds on Tuesday, Mr Trump said: “This is historic, it’s epic, what happened. But you know what? It happened in Texas and Texas can handle anything.”
The US president then held a Texan flag aloft, sparking loud cheering from the crowd.
The storm marks the first time Mr Trump has been tested by a major natural disaster.
On Monday, he said “every asset at his command” was available to help those affected by the storm.
The president said that federal cash for storm-ravaged areas will arrive quickly.
“To the people of Texas and Louisiana, we are 100% with you,” Mr Trump said.