© Ted Jackson/AP
Rescuers and civilians work to pull people from their flooded homes near Amite in Louisiana, where a state of emergency has been declared.
Governor John Bel Edwards said residents had been pulled from swamped cars, flooded homes and threatened hospitals across the southern part of the state. The already soaked region is expected to get more rain from a storm system stretching from the Gulf Coast to the Ohio Valley.
While the brunt of the storm that brought torrential rains was moving west toward Texas, 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, calling the flooding unprecedented.
Obama issued the disaster declaration after speaking with Edwards, the White House said in a statement.
The initial declaration makes federal aid available in the parishes of East Baton Rouge, Livingston, St. Helena and Tangipahoa. Edwards said in a statement that other parishes could be added to the list.
Emergency officials still were working on strategies to rescue an undetermined number of people trapped by the waters.
Comment: Governor Edwards declared a state of emergency over the weekend, calling the floods 'unprecedented' and 'historic'. Some other 'historic' flooding in the United States in recent times include:
June 2016: 23 deaths as West Virginia swamped
March 2016: more 'historic' flooding in the southern states
January 2016: massive flooding and mudslides in southern California
November 2015: record rainfall in Texas
October 2015: "once-in-a-thousand-year" flash flooding in South Carolina