New Orleans officials have imposed a citywide curfew as large parts of Louisiana and Mississippi remain without power following Hurricane Ida.
Mayor LaToya Cantrell said the curfew would last from 20:00 to 06:00 and police said there had been “several” incidents of looting in the city.
Energy companies are working to restore power but residents are being warned it could take weeks in some areas.
Meanwhile water services and infrastructure have also been hit.
Two people were killed and at least 10 injured after a section of highway collapsed near Lucedale, Mississippi on Monday.
Several cars were reported to have fallen into a hole that was 50 to 60ft (15 to 18m) long and 20 to 30ft deep, according to highway police.
Local authorities believe that some of the drivers may not have been able to see the road properly because of the heavy rains. The highway remains closed.
Over eight inches (20cm) of rain fell in the area during Ida, which reached the US mainland as a Category 4 storm on Sunday.
While Ida’s speed has slowed, authorities continue to warn of storm surges and heavy rains across the southern US.
By Tuesday afternoon, Ida was in Tennessee, soaking the area with intense rain and prompting flash flood warnings.
Local officials have urged evacuated residents to delay their return home as more than one million homes and businesses remain without power, including most of New Orleans.
Mayor Cantrell said that she was hopeful “that we should have some level of transmission” by Wednesday but “that does not mean we will immediately see all the lights on in the city.”
Federal officials say that some 441,000 people in 17 parishes across the region have no water, and a similar number may be without power for up to a month.
It comes as heat advisories have been issued, with some areas expected to reach 95F (35C), according to weather officials say.
Louisiana Governor John Bel Edwards said some 25,000 line workers were working to restore power but admitted: “There are an awful lot of unknowns right now.”
Meanwhile Louisiana Lieutenant Governor Bill Nungesser has warned the death toll from Ida will likely rise in the coming days.
In addition to the two killed during the highway collapse, at least two other people have been reported dead during the storm.
In Louisiana, a man died while attempting to drive across a flooded area of New Orleans. Another man died after being struck by a tree near Baton Rouge.
“Knowing that so many people stayed behind in places like Grande Isle and Lafitte where flood waters have devastated those areas, we expect there will be more people found who have passed,” Mr Nungesser said.
Ida is expected to move next to the US northeast, with rain and threat of floods stretching from the Tennessee to the mid-Atlantic.
Washington, DC, Baltimore and Philadelphia are among the cities now under flash flood watches.