US President Joe Biden has deployed an additional 1,000 active-duty soldiers to bolster aid efforts in the south-eastern US, after the region was pummelled by Hurricane Helene.

These soldiers will join the 6,000 National Guard members and 4,800 federal aid workers already fanned out across six states hit by extreme weather.

At least 175 people are now known to have been killed by Hurricane Helene, one of the deadliest storms to hit the US in recent times.

Hundreds of others remain missing, with search and rescue teams struggling to reach remote areas.

Aid deliveries have been made by airdrops and mules. The US government has said the clear-up effort could take years.

Biden is due to visit the badly-affected North Carolina and South Carolina states, while Vice-President Kamala Harris goes to neighbouring Georgia.

Both happen to be key swing states in November?s presidential election ? and the storm has already become political after Republican presidential nominee Donald Trump took his own trip to Georgia earlier in the week.

Helene hit the US on Thursday as a Category 4 hurricane ? the most powerful on record to strike Florida?s Big Bend ? before tearing through neighbouring states and downgrading to a tropical storm.

The scale of the rainclouds were unusual, and the storm lingered for relatively long periods. Saturated ground from previous rains was also an aggravating factor.

The BBC's US partner CBS News has reported 175 deaths, recorded across six states: North Carolina, South Carolina, Georgia, Florida, Tennessee and Virginia.

The toll surpasses that of Hurricane Ian, which in September 2022 became another of the 21st Century?s deadliest storms ? claiming at least 156 lives.

According to CBS, almost half of the deaths caused by Helene have been in North Carolina alone, where six months? worth of rain fell.

The state?s mountainous areas suffered particularly heavy rain ? as is typical in storm conditions ? which resulted in homes and bridges being washed away.

One emergency official in Buncombe County ? which includes the hard-hit city of Asheville ? said the state had experienced ?biblical devastation?.

A volunteer Involved in relief efforts told the BBC on Tuesday they knew someone who had ?lost everything? in Hurricane Katrina in 2005, and had moved to Asheville, only to be devastated again nearly two decades later.

?Looks like she?s wiped out again,? the volunteer said. ?She has no drinking water. No gasoline. The food in her fridge has rotted.?

The extreme weather has also forced the closure of mines in Spruce Pine, a small town that is home to the world?s largest-known source of high-purity quartz.

In Tennessee, state authorities are investigating the operator of a plastics factory where 11 workers were swept away by rushing floodwaters on Friday. Five of the employees were rescued. Two have been confirmed dead and four more remain missing.

Impact Plastics told CBS in a statement it had monitored weather conditions around its Erwin plant in north-eastern Tennessee, and dismissed employees ?when water began to cover the parking lot and the adjacent service road, and the plant lost power?.

But in interviews with local outlets, employees said they were allegedly told to continue work in the factory until it was too late for a safe exit.

Jacob Ingram, a mold changer at the factory, filmed himself and four others waiting for rescue as vehicles and debris were carried away by the muddy water surrounding him.

?I was working at impact when the storm hit yesterday,? Mr Ingram wrote in a post on Facebook, adding he and 11 others were trapped on the back of a semi-truck. ?I?m lucky to be alive.?

Rebuilding efforts could take years, Homeland Security Secretary Alejandro Mayorkas has said. Biden has allowed survivors to apply for federal assistance money by making disaster declarations in various states.

On Monday, Biden referenced reports that up to 600 people were unaccounted for. ?God willing, they?re alive,? he said. ?But there?s no way to contact them again because of the lack of cell phone coverage.?

More than a million people in some of the affected states also remained without power on Wednesday morning, according to monitoring site Poweroutage.us.

Initial analysis of the storm already suggests that human-induced climate change played a significant role in the amount of rainfall that was dumped.

After Helene hit late on Thursday, record flood crests were measured in at least seven locations in North Carolina and Tennessee.

In parts of western North Carolina, records that had stood since the ?Great Flood? of July 1916 were smashed.

The Atlantic hurricane season continues until the end of November. The waters of the Gulf of Mexico and Caribbean are currently above average temperatures, meaning that it is possible that still more powerful storms could develop. (BBC)

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