Watch: Moment building and container swept away by Helene

Eyewitness video from Asheville in North Carolina captured the moment that parts of a building and a shipping container were swept away in floodwaters caused by Tropical Storm Helene.

Debris from the building belonging the Asheville Tea Company broke-up upon impact with an electrical pole. The shipping container folded over the pole upon impact.

More than 210 people are now confirmed dead after Helene carved a path of destruction through several US states, officials said, making it the second deadliest storm to hit the US mainland in more than half a century.

Helene came ashore in Florida last week as a major Category 4 hurricane.

It pulverized many communities nestled in the forested Blue Ridge Mountains of western North Carolina and neighboring Tennessee. Restoring roads and power and water systems will take weeks or months.

US President Joe Biden made his second straight day of visits to the country's southeast to grieve with residents of a region traumatised by a disaster that has upended life for millions.

The storm flooded towns and cities, made countless roads impassable, knocked out power and water service, and left communities shell-shocked as they grapple with the start of a years-long recovery effort.

More than half of the deaths were in flood-ravaged North Carolina, which is experiencing an unprecedented disaster described by some as post-apocalyptic.

"I see you, I hear you, I grieve with you - and I promise you, we have your back," Mr Biden said during a stop at a damaged pecan farm in Ray City, Georgia.

Helene is the deadliest hurricane to hit the US mainland since 2005's Katrina, which killed 1,392 people.

Despite hundreds of rescues across six states and an enormous response including thousands of federal personnel and thousands more National Guard members and active-duty troops assisting local responders, the death toll from the sprawling storm is expected to rise.

Many residents are still unaccounted for in a mountainous region known for its pockets of isolation.

"We are continuing to find survivors," North Carolina's Buncombe County, the epicentre of the tragedy where more than 70 people are confirmed dead, said in its latest update, adding there are residents still cut off from the outside world due to landslides and destroyed bridges.

In Asheville, a city of about 100,000 at the foot of picturesque mountains, and popular with tourists, thick mud covers streets. Buildings and other structures along riverbanks have been washed away.

Authorities are pursuing their desperate search for survivors in remote areas, while downtown, restaurants and aid groups are providing free food and water. Repair crews are struggling to restore power to hundreds of thousands of customers still without electricity.