Torrential rain from Storm Helene has ravaged parts of North Carolina and Tennessee – the latest south-eastern US states to suffer in a disaster that has killed at least 63 people.

In North Carolina the mountain city of Asheville was largely cut off by flooding on Saturday, the BBC’s US partner CBS News reported.

More than 400 roads remain closed in the state, where 10 people have died. Supplies are being airlifted to residents, state Governor Roy Cooper said.

Officials have continued daring rescues with boats, helicopters and large vehicles to help those stranded in floodwaters – including about 50 workers and patients who crowded on the roof of a flooded Tennessee hospital.

Many petrol stations are closed in North Carolina with long queues of cars at those still open. Power cuts have hit at least three million customers across five states.

The storm began as a hurricane – the most powerful on record to hit Florida’s Big Bend, and moved north into Georgia and the Carolinas after making landfall overnight on Thursday.

In pictures: Hurricane Helene destruction

Although Helene has weakened significantly, forecasters warn that high winds, flooding and the threat of tornadoes could continue.

The damage is estimated at between $95bn and $110bn (£71bn-£82bn). Governor Cooper called it “one of the worst storms in modern history” to hit North Carolina.

Asheville, home to about 94,000 people and a popular tourism and arts hub, was swamped and eerily quiet on Saturday, CBS reported.

The search for survivors is going on and federal emergencies have been declared in six states including Florida and Georgia.

In Tennessee, 58 patients and staff were left stranded on the roof of a hospital in the city of Erwin on Friday. Swift-moving water from the Nolichucky river prevented boats from conducting rescues, and high winds prevented helicopter operations.

The group was later taken to safety after helicopters from the Tennessee National Guard and the Virginia State Police intervened.

“The devastation we’re witnessing in Hurricane Helene’s wake has been overwhelming,” President Joe Biden said on Saturday.

He was briefed by Deanne Criswell, head of the Federal Emergency Management Agency, whom he directed to speed up support to storm survivors, including deployment of extra teams to North Carolina.

There could be as many as 25 named storms in 2024, the National Oceanic and Atmospheric Administration warned earlier this year.

Between eight and 13 of those storms could develop into hurricanes and a handful already have including Helene.

More storms could be on the horizon, officials warned, as the official end of hurricane season is not until 30 November.