Hurricane Matthew killed 1,000 people in Haiti and at least 19 in the United States before downgrading to a post-tropical cyclone.

The storm moved out to sea Monday after hitting the coasts of North Carolina and Virginia, staying clear of the Northeast, the National Hurricane Center said. 

Matthew, the most powerful Atlantic storm since 2007, made landfall near McClellanville, South Carolina, a village 30 miles north of Charleston, on Saturday, after slamming the coasts of Florida and Georgia with strong winds and rain. 

Residents of the states hit by the storm turned their focus on Monday toward recovery and clean-up, but officials warned that deadly flooding could continue as swollen rivers crest in the coming days.

With five people reported missing and rivers rising, North Carolina Governor Pat McCrory said he expected the death toll to rise. Eight people in the state were known to have died so far.

McCrory said several swelling rivers were expected to hit record levels and would not crest for days.

"Hurricane Matthew is off the map, but it is still with us and it is still deadly," he said.

The National Weather Service said "life-threatening flooding" would continue on Monday over eastern portions of the state.

Many coastal and inland communities remained under water, either from coastal storm surge or overrun rivers and creeks.

U.S. President Barack Obama declared a state of emergency in Georgia and Florida, freeing up federal money to help the states repair damaged infrastructure and remove debris.

DEVASTATION IN HAITI

Haiti started burying some of its dead in mass graves in the wake of Hurricane Matthew, a government official said on Sunday, as cholera spread in the devastated southwest and the death toll from the storm rose to 1,000 people.

The official death toll from the central civil protection agency is 336, a slower count because officials must visit each village to confirm the numbers.

Authorities had to start burying the dead in mass graves in Jeremie because the bodies were starting to decompose, said Kedner Frenel, the most senior central government official in the Grand'Anse region on Haiti's western peninsula.

Frenel said 522 people were killed in Grand'Anse alone. A tally of deaths reported by mayors from 15 of 18 municipalities in Sud Department on the south side of the peninsula showed 386 people there. In the rest of the country, 92 people were killed, the same tally showed.

Frenel said there was great concern about cholera spreading, and that authorities were focused on getting water, food and medication to the thousands of people living in shelters.

Cholera causes severe diarrhea and can kill within hours if untreated. It is spread through contaminated water and has a short incubation period, which leads to rapid outbreaks.

Government teams fanned out across the hard-hit southwestern tip of the country over the weekend to repair treatment centers and reach the epicenter of one outbreak.