Three dead, over 7000 rescued from deadly Louisiana flood waters
The Acadian Thruway is covered in floodwaters in this handout picture from the Louisiana Department of Transportation and Development taken in Baton Rouge, Louisiana, U.S. August 12, 2016. Louisiana Department of Transportation and Development/Handout via Reuters

Emergency crews have rescued more than 7,000 people stranded in Louisiana by historic flooding that has killed at least three people and submerged whole communities, Governor John Bel Edwards said on Sunday, as the U.S. Gulf Coast braced for more rain and rising waters.

Stranded residents have been pulled out of flooded homes and swamped cars in cities and towns across the southern part of the state, said Edwards, who has called for federal emergency relief funds.

While the brunt of the storm that brought torrential rains and flooding to the area was moving west toward Texas on Sunday, Louisiana residents should remain cautious, the governor said at a news conference.

"Even with the sunshine out today intermittently, the waters are going to continue to rise in many areas, so this is no time to let the guard down," Edwards said.

Some 5,000 people were forced to sleep in shelters overnight, state officials said. There were not enough beds to house all of the shelter-seekers, so many had to sleep on floors.

Emergency officials were still working on strategies to rescue an undetermined number of other people trapped by the waters, Edwards said.

Meanwhile, downpours threatened to trigger floods further west into Texas.

The National Weather Service (NWS) on Sunday maintained a flash flood watch for parts of Louisiana and Mississippi and extended it to southeastern Texas, including the city of Houston, where rains left at least eight dead in late April.

More rains were expected in southern Louisiana, with NWS forecasting on its website that another 2-6 inches (5-15 cm) were possible on Sunday night in some areas, while 2-4 inches could fall in others and in parts of Texas.

Edwards, who described the flooding as "unprecedented" and "historic," said he was awaiting a response to his request that the Federal Emergency Management Agency (FEMA) make a federal disaster declaration for affected areas of the state.

He declared a state of emergency on Friday as rivers began to spill over.

In addition to the three dead in the flooding, another person is believed to be missing, Edwards said.

On Saturday, the body of a woman was recovered from the Tickfaw River in St. Helena Parish, northeast of Baton Rouge near the Mississippi border.

Michael Martin, chief of operations for the parish sheriff's office, said the woman was riding in a car with her husband and his mother when flood waters swept the vehicle into the river. Rescuers found the two others clinging to a tree on Saturday.

A 54-year-old man in Greensburg in the northern part of the state died when his vehicle was swept off the road, a Louisiana State Police spokeswoman said in a statement on Saturday.

The body of a 68-year-old man was recovered on Friday near Baker, Louisiana, close to the state capital, after he drowned while trying to evacuate, said William "Beau" Clark, the coroner in East Baton Rouge Parish.

(Additional reporting by Chris Prentice and Laila Kearney in New York; Editing by Frank McGurty and Alan Crosby)