BATON ROUGE, La., (UPI) — The U.S. federal government on Sunday declared a major disaster for parts of Louisiana after heavy rainfall and “unprecedented” flooding that killed at least six people.

Louisiana’s parishes of Tangipahoa, St. Helena, East Baton Rouge and Livingston were the first to be named as major disaster areas. More parishes may be declared disaster areas after the damage is assessed.

An elderly man drowned Saturday after falling into deep water in East Baton Rouge, while another man died when his pickup truck was swept off a highway and submerged in flood waters. The corpse of a woman was recovered from the Tickfaw River.

About 20,000 people have been rescued from flooding in south Louisiana after some parts saw between 10 to 26 inches of rain in a 24-hour period. At least 10,000 people were in emergency shelters as of Sunday night. Nearly 40,000 people were left without power. At least 1,000 Louisiana National Guard members were deployed to assist in rescue efforts.

Louisiana Gov. John Bel Edwards on Friday declared a state of emergency for the whole state. On Sunday, Edwards asked for federal assistance to pay for emergency operations and overtime. President Barack Obama agreed by declaring a major disaster in the four parishes.

“I have traveled to affected areas and have seen the destruction caused by this unprecedented flooding,” Edwards said in a statement. “We are thankful for the federal government’s quick response to our request for an emergency declaration. This is an ongoing event, and we are confident that every available state and federal resource will be brought to bear. I fully expect that more parishes will be added to the declaration on a rolling basis.”

Edwards has asked Louisiana residents to stay at home and to avoid roads, many of which are hazardous, unless residents “absolutely have to be on the road.”