Remnants of Hurricane Laura unleashed heavy rain and twisters hundreds of miles inland from a path of death and mangled buildings along the US Gulf Coast, and forecasters warned an eastern turn would again make the storm a looming threat, this time to the densely populated Eastern Seaboard.

Trees were down and power was out as far north as Arkansas, where remnants of the storm that killed at least six people in the United States were centred. The once fearsome Category 4 hurricane packing 150-mph winds weakened to a depression after dark.

New tornado warnings were issued after nightfall in Mississippi and Arkansas, hours after one of the strongest hurricanes ever to strike the United States barrelled across Louisiana on Thursday.

A reported tornado tore part of the roof from a church in rural northeastern Arkansas as the remnants of Hurricane Laura crossed the state. No injuries were reported but the system still packed a punch after smashing into Louisiana’s Gulf Coast near the line with Texas.

A full assessment of the damage could take days. By then, the storm could re-energize and pose a threat to several Northeast states by Saturday, forecasters said.

Despite demolished buildings, entire neighbourhoods left in ruins and almost 900,000 homes and businesses without power along the coast, a sense of relief prevailed that Laura was not the annihilating menace forecasters had feared.

“It is clear that we did not sustain and suffer the absolute, catastrophic damage that we thought was likely,” Louisiana Gov. John Bel Edwards said. “But we have sustained a tremendous amount of damage.”

He called Laura the most powerful hurricane to strike Louisiana, meaning it surpassed even Katrina, which was a Category 3 storm when it hit in 2005.

The hurricane’s top wind speed of 150 mph (241 kph) put it among the strongest systems on record in the US. Not until 11 hours after landfall did Laura finally lose hurricane status as it plowed north and thrashed Arkansas, and even up until Thursday evening, it remained a tropical storm with winds of 40 mph (65 kph).

The storm crashed ashore in low-lying Louisiana and clobbered Lake Charles, an industrial and casino city of 80,000 people. On Broad Street, many buildings had partially collapsed. Windows were blown out, awnings ripped away and trees split in eerily misshapen ways. A floating casino came unmoored and hit a bridge, and small planes were thrown atop each other at the airport.

In front of the courthouse was a Confederate statue that local officials had voted to keep in place just days earlier. Laura knocked it down.

“It looks like 1,000 tornadoes went through here. It’s just destruction everywhere,” said Brett Geymann, who rode out the storm with three relatives in Moss Bluff, near Lake Charles. He described a roar like a jet engine as Laura passing over his house around 2 a.m.

“There are houses that are totally gone,” he said.

As the extent of the damage came into focus, a massive plume of smoke visible for miles began rising from a chemical plant. Police said the leak was at a facility run by Biolab, which manufactures chemicals used in household cleaners and chlorine powder for pools. Nearby residents were told to close their doors and windows, and the fire smouldered into the night.

The fatalities included a 14-year-old girl and a 68-year-old man who died when trees fell on their homes in Louisiana, as well as a 24-year-old man who died of carbon monoxide poisoning from a generator inside his residence. Another man drowned in a boat that sank during the storm, authorities said.

No deaths had been confirmed in Texas, which Republican Gov. Greg Abbott called “a miracle.”

It was unclear when the journey home would be complete for more than 580,000 coastal residents who evacuated under the shadow of a coronavirus pandemic. Although not everyone fled, officials credited those who did leave with minimizing the loss of life.

A lower-than-expected storm surge also helped save lives. Edwards said ocean water rose as much as 12 feet (4 metres) rather than the 20 feet (6 metres) that was predicted.

Finishing search and rescue efforts was a top priority, Edwards said, followed by efforts to find hotel or motel rooms for those unable to stay in their homes. Officials in Texas and Louisiana both sought to avoid traditional mass shelters for evacuees over fears of spreading COVID-19.

Laura’s winds blew out every window of the living room in the Lake Charles house where Bethany Agosto survived the storm with her sister and two others. They huddled in a closet, where she said, “it was like a jigsaw puzzle…we were on top of each other, just holding each other and crying.”

Laura was the seventh named storm to strike the US this year, setting a new record for U.S. landfalls by the end of August. Laura hit the US after killing nearly two dozen people on the island of Hispaniola, including 20 in Haiti and three in the Dominican Republic.

Donald Trump planned to visit the Gulf Coast this weekend to tour the damage.