More than 13,000 rescued as Tropical Storm Harvey leaves 18 dead

At least 18 people have died and 13,000 more have been rescued as Tropical Storm Harvey dumps record rainfall in and around Houston.

As thousands of people fled their deluged homes, Houston's mayor Sylvester Turner, imposed a curfew amid reports of looting and armed robberies.

Officials say they have received disturbing reports of people impersonating Homeland Security special agents and telling residents to evacuate in order to rob their homes.

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The heaviest tropical downpour in US history has left an area 15 times the size of Manhattan under water.

City officials readied temporary housing for about 19,000 people, with thousands more expected to flee as flooding entered its fourth day and space ran out in cramped shelters.

SEE ALSO: Dominica PM expresses ’empathy and solidarity’ as Texas battles floods

Louisiana in path

With many reported missing, the number of dead is expected to rise once floodwaters start to recede.

The National Hurricane Center, based in Miami, says the storm has now made a second landfall.

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This time it has hit Louisiana, a state that still bears deep scars from deadly Hurricane Katrina in 2005.

It is expected to produce an additional 15cm to 30cm (6in to 12in) of rain to the north and east of Houston as it moves into southwestern Louisiana.

The tropical storm is projected to weaken as it moves inland to the north east and over Mississippi by Thursday.

President Donald Trump visited the affected area on Tuesday, telling rescue organisers: "This was of epic proportion, nobody has ever seen anything like this."

The president paid a visit to Corpus Christi, where the storm made landfall. He will not travel to Houston.

Billions in damage

On Tuesday, residents within 1.5 miles (2.4km) of a chemical plant in Crosby were ordered to evacuate due to the rising risk of an explosion and subsequent leak.

A breached levee south of Houston and two overflowing reservoir dams outside the city are also adding to the rising water levels.

The National Hurricane Center warned of "ongoing catastrophic and life-threatening flooding" continuing across south eastern Texas.

And the National Weather Service warned of dangerous flash flooding pushing northeast over the coming days.

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Rescue services say that make-shift shelters are beginning to run out of space. 'Mega-shelters' are being planned to accommodate evacuees in Houston.

With rescue services overstretched, civilians with boats and trucks are responding to calls for help and helping saving lives.

On Wednesday, Singapore's defence ministry sent four military helicopters to assist with the relief effort, airlifting troops, evacuees and supplies.

Damage is expected to run into tens of billions of dollars, making it one of America's most expensive natural disasters.