Donald Trump has asked Congress for $7.9 billion (£6bn) to provide initial relief for areas affected by Hurricane Harvey.

Texas and Louisiana have been worst hit by the storm, with heavy flooding affecting both states, and the death toll has risen to 42 one week after Harvey hit the Gulf coast.

Authorities are continuing to go door-to-door in flood-hit areas, while some people are being allowed to return to their homes.

As well as the flooding, there has been a shortage of drinking water in some places. In Beaumont, Texas, people waited in a line that stretched for more than a mile to get bottled water.

The president and his wife Melania will make their second visit to Texas on Saturday. Mr Trump has pledged $1m of his personal fortune to help victims of the storm.

His request for relief funds, which is expected to be swiftly approved by Congress, would add $7.4bn (£5.7bn) to rapidly dwindling Federal Emergency Management Agency (FEMA) disaster aid coffers and $450 million (£347m) to finance disaster loans for small businesses.

The request also reiterates the need for Congress to increase the Government's $19.9 trillion (£15tn) borrowing limit by the end of this month. Republicans are signalling that they may link the unpopular debt limit increase to Harvey relief.

House Speaker Paul Ryan said nothing will stop a Harvey aid bill from getting through Congress.

He said a storm the size of Harvey is unprecedented and because of that it "deserves and requires federal response".

The White House says more than 436,000 households have registered for federal assistance.

The initial Harvey aid package would replenish FEMA disaster funds until September 30.

A larger aid package is likely to be put together before the end of the year.

It is feared the full-scale of the disaster could exceed the damage from 2005's Hurricane Katrina, which cost taxpayers $110bn (£85bn).

There is still at risk of flooding as a result of Harvey as far north as Indiana.

In Houston, officials tried to protect parts of the devastated city by deliberately flooding others.

The mayor announced plans to release water from two reservoirs that could keep as many as 20,000 homes flooded for up to 15 days.

As well as the risk from flooding, there have been concerns surrounding a Houston-area chemical plant, where highly unstable compounds blew up after losing refrigeration.

Thick black smoke and towering orange flames have been seen coming from the Arkema plant in Crosby for two days.

The Environmental Protection Agency and local officials said there was no reason for alarm and no serious injuries were reported, but authorities have evacuated an area around the plant.

Harvey initially made landfall on August 25 as a Category 4 hurricane, then went back out to sea and lingered off the coast as a tropical storm for days. The storm brought five straight days of rain totaling close to 52 inches in one location, the heaviest tropical downpour ever recorded in the continental US.

National Weather Service meteorologists expect Harvey to break up and merge with other weather systems over the Ohio Valley late on Saturday or Sunday.