(Adds additional death and other details on flooding)

By Carlo Allegri and Gene Cherry

LUMBERTON, N.C./KINSTON, N.C., Oct 11 (Reuters) – Flooding in the aftermath of Hurricane Matthew has displaced several thousand people in North Carolina, and authorities were helping more evacuate on Tuesday as swollen rivers threatened a wide swath of the state.

Governor Pat McCrory warned of “extremely dangerous” conditions in the coming days in central and eastern North Carolina, where several rivers were at record or near-record levels.

Matthew, the most powerful Atlantic storm since 2007, killed at least 1,000 people in Haiti last week before barreling up the U.S. southeastern coast and causing at least 30 deaths in Florida, Georgia and the Carolinas.

McCrory’s office said four additional deaths were confirmed on Tuesday in North Carolina, raising the death toll in the state to 18. One person was reported as missing.

An additional U.S. death occurred on Monday night in Lumberton, North Carolina, where officials said a highway patrol officer fatally shot a man who became hostile and flashed a handgun during search-and-rescue efforts in fast-running floodwater.

Nearly 4,000 people have taken refuge in North Carolina shelters, including about 1,200 people in the hard-hit Lumberton area, where the Lumber River had crested at almost 4 feet (1.2 meters) above the prior record set in 2004 after Hurricane Frances.

Water blanketed the city of 21,000 people, leaving businesses flooded, homes with water up to their roof lines and drivers stranded after a stretch of Interstate-95 became impassable.

“We lost everything,” said Sarah McCallum, 62, who was staying in a shelter set up in an agricultural center after floodwaters drove her from her home of 20 years.

State officials are particularly concerned about victims like McCallum, who have no flood insurance because they do not live in areas typically prone to inundation. U.S. President Barack Obama on Monday signed a disaster declaration for North Carolina, which will make federal funding available to people in the hardest-hit areas.

Obama approved a similar declaration on Tuesday for South Carolina, where Matthew made landfall on Saturday. State officials are now urging residents to prepare for potential flooding from the Waccamaw and Little Pee Dee rivers.

About 532,000 homes and businesses remained without power in the U.S. Southeast on Tuesday, down from the peak of around 2.2 million on Sunday morning when the storm was still battering the Carolina coasts.

WORST FLOODING SINCE FLOYD

Matthew dumped more than a foot (30 cm) of rain in areas of North Carolina already soaked from heavy September rainfall. Ithas triggered the worst flooding in the state since Hurricane Floyd in September 1999, the National Weather Service said.

That storm caused devastating floods in North Carolina, resulting in 35 deaths, 7,000 destroyed homes and more than $3 billion in damages in the state.

In Matthew’s wake, officials are monitoring a number of overtopped or breaching dams in addition to the threat of inland river flooding, the governor’s office said.

Concerns about a potential breach of the Woodlake Dam, which led to overnight evacuations in the central North Carolina town of Spring Lake, had eased by Tuesday afternoon after it was reinforced with 700 sandbags, but a mandatory evacuation was still in effect for nearby residents.

McCrory warned that the Tar River was expected to crest on Wednesday in Greenville, where a mandatory evacuation order is already in place.

Officials remain concerned about Kinston, where significant flooding was already occurring from the Neuse River, which is expected to crest at about 27 feet (8 meters) on Saturday, just shy of the Floyd record.

Retired construction worker Wesley Turner, 71, said he fled his home near Kinston with his dogs on Friday after his power went out and the water quickly rose to about chest deep.

After several nights in a shelter, he did not know on Tuesday whether he had anything to return to.

“I can’t get to my house because it is under water,” Turner said.

(Additional reporting by Letitia Stein and Joseph Ax; Writing by Colleen Jenkins; Editing by Bill Trott, Tom Brown and Bill Rigby)