BATON ROUGE • Louisiana has been hit by epic flooding, with seven people killed and thousands evacuated to emergency shelters after waterways in the southern part of the state overflowed their banks.
Some areas have received more than 50cm of rain since late Thursday, submerging vast swathes of southern Louisiana in muddy waters.
"Our state is currently experiencing a historic flooding event that is breaking every record," Louisiana Governor John Bel Edwards said in a statement late on Monday. "This event is ongoing, it is not over. We do not know when the flood waters will recede, and they will continue to rise in some areas."
About 30,000 people had been rescued, including a 78-year-old woman who spent a night in a tree, police told CNN.
There were 14,000 people staying in shelters, mostly in the state capital Baton Rouge and surrounding communities.
Police said the Louisiana National Guard would assist evacuees in the massive shelters, which included a Baton Rouge film studio complex and an entertainment centre in the city's downtown area.
A helicopter survey late on Monday by the East Baton Rouge Sheriff's Office showed large areas of submerged land. Seven people were confirmed dead, said the police, noting that the toll could rise in the coming days.
Some 40,000 homes and business were reported without power.
The White House declared four parishes - equivalent to counties in other states - major disaster areas.
The National Weather Service (NWS) continued to issue flood warnings in effect through early yesterday, saying water in many areas would not recede at least for another day.
The Amite River, the source of flooding in many areas, had risen 4.3m above flood level in one reading, besting a previous record flood in April 1983, the NWS said.
Officials reported that hundreds of roads, mostly in the southern parts of the state, were closed.
The White House action makes emergency federal funding available to support rescue crews and recovery efforts. The Federal Emergency Management Agency on Monday began asking those affected by the floods to apply for assistance, and officials said 11,000 people had already registered early in the day.
The American Red Cross said that it was responding to the disaster, which it called the worst since Superstorm Sandy flooded coastal areas of New York and New Jersey in 2012.
Many parishes in Louisiana were collecting donations for flood victims, including food, water, blankets and hygiene products.
The Louisiana National Guard reported that its soldiers rescued nearly 500 people and 61 pets in 24 hours over Friday and Saturday, by boat, helicopter and high-water (high-clearance) vehicles.
The NWS said other areas of the US faced threats of flash floods - from the Texas coast to the Ohio River Valley. The storms threatening Texas were part of the same system that deluged Louisiana, although it was now less potent, said NWS meteorologist Gavin Phillips.