The US city of Houston is in the grip of the biggest storm in the history of the state of Texas, officials say.
A record 30in of rain (75cm) has fallen on the city in the wake of Hurricane Harvey, turning roads into rivers.
The area is expected to have received a year’s rainfall within a week. Five people are reported dead. Helicopters have plucked victims from rooftops.
With rescue services overstretched as the rain continues, many people are having to fend for themselves.
Harvey made landfall as a category-four hurricane late on Friday. It was later downgraded to a tropical storm.
Up to 2,000 people have been rescued in and around Houston, the fourth-largest city in the US, where about 6.6m people live in the metropolitan area.
In Washington, the Federal Emergency Management Agency (Fema) said it was committed to assisting in the rescue effort.
Fema administrator Brock Long said providing shelter to 30,000 people in need was “going to be a very heavy lift”. He added that the agency was also working to restore power and critical infrastructure.
Thousands of homes are without electricity. Many schools are closed – as are the two main airports, with runways completely flooded.
An inundated care home in Dickinson, about 30 miles (50 km) south east of the city, has now been evacuated by helicopter after an image of several elderly women sitting in a lounge in waist-deep water went viral on social media.
A city in crisis – James Cook, BBC News, Houston
Entire suburbs are under water, shops and businesses are shut and, with the motorways around the city cut off and both airports closed, travel is all but impossible.
A marooned hospital has been evacuated while, above the city, engineers are starting an emergency release of water from two bulging dams.
They are warning families who live beside one of the dams to prepare for flooding within hours.
Some residents have been critical of the preparations for this storm, which intensified rapidly in the Gulf of Mexico last week.
In at least one neighbourhood facing severe flooding, people are angry that they were told to stay put only to realise, as night fell, that the waters were rising fast and they could not get out.
The authorities are being stretched to breaking point. It is difficult to see how they could accommodate President Donald Trump, who plans to visit Texas on Tuesday.
If he does decide to travel here, he will find a powerful oil city on its knees.
Is flooding showing signs of easing?
No. As the storm continues to batter south-eastern Texas, swelling rivers are causing a surge that is heading for Houston.
Houston Mayor Sylvester Turner told residents: “Don’t get on the road. Don’t assume this storm is over.”
Tens of thousands of people have been were ordered to leave parts of Fort Bend County, about 35 miles (55 km) south-west of Houston, where a river is set to crest this week.
Houston authorities, however, have not issued a mass evacuation order.
Mayor Turner on Sunday defended the decision by citing the “crazy” logistics of planning an evacuation of 2.3 million people.
He cited the chaos Houston experienced when residents were evacuated ahead of Hurricane Rita in September 2005. People were stuck for more than 20 hours on gridlocked road, resulting in dozens of deaths.
Rita, which had been predicted to hit Houston, passed well east of the city.
Observers also recalled the disastrous evacuation ahead of Hurricane Katrina, which hit New Orleans in August that year. Thousands of people spent days in squalid conditions and limited water at that city’s stadium.
What are the economic consequences from Harvey?
The Texas Gulf Coast is a key centre of the US oil and gas industry, and some of the largest refineries in the country have halted operations.
This has raised concerns about fuel shortages and higher prices at the pump.
The wider economic damage from Harvey is being assessed.
Insurance experts quoted by Reuters news agency say it could equal the devastation inflicted by Hurricane Katrina – reportedly the most expensive natural disaster in US history.
Katrina caused about $15bn (£11.6bn) of flood damage in the states of Louisiana and Mississippi.
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