(CNN) -- The warning system intended to notify campers on federal land about potentially devastating weather will be re-examined in Arkansas and throughout the nation, U.S. Agriculture Secretary Tom Vilsack said Saturday.
Vilsack's announcement came as rescue workers were continuing to search for people still missing after flash flooding killed at least 18 people at the Albert Pike Recreation Area. The park is along the Caddo and Little Missouri rivers in western Arkansas.
Authorities released the names of 15 of the dead Saturday, with six children among the victims, including one girl as young as 2. Several groups of people with the same last name also were listed.
The victims identified were largely from Texas and Louisiana. One person was from Foreman, Arkansas. Ages of the adult victims ranged from 23 to 69.
Before the storm, which hit about 2 a.m. Friday, campers could have called forest officials or checked the campground's website. But the flooding occurred when most campers were sleeping and "it came so suddenly," an official said there's little chance anyone had time to escape.
The park normally has spotty television and cell phone service, making warnings even more difficult to communicate, U.S. Sen. Blanche Lincoln, D-Arkansas, added.
Meanwhile, crews continued looking for trapped people and bodies using horses, all-terrain vehicles and canoes to fan out across the rugged region. The search had been suspended Friday night.
Rescuers are combing through riverbanks again and expanding the search after floodwaters have begun to recede, said John Strom, safety officer with the U.S. Forest Service.
As of midafternoon Saturday, 16 of the dead had been identified, said Capt. Mike Fletcher of the Arkansas State Police.
Four people were confirmed missing from the campsite area, Gov. Mike Beebe said Saturday. There are 20 other individuals who also may have been camping in the area or at other nearby sites.
Some of the 18 dead are children, Beebe said.
Brigette Williams of the American Red Cross asked relatives looking for missing family members as well as flood survivors to register at a Red Cross website created to help connect families affected.
The Red Cross initially estimated as many as 300 people had been in the Albert Pike campground area, a part of the U.S. Forest Service, Beebe said. He cautioned there was no way to be certain about that number. A list the park kept of registered campers was washed out, officials have said.
At a press conference Saturday, Beebe described trucks being wrapped around trees "and other vehicles and [RVs] that have been flipped upside down and thrown around like they were toys by the pure power of that water."
Beebe said the Little Missouri River rose at the campground from about 3 feet Thursday night to more than 20 feet early Friday.
"It's like a canyon, where all that water comes down from the mountains and just goes and is funneled into a small area," he said. "And the river rose very quickly."
"As the water has gone down we are able to find more vehicles, which allows us to trace the license [plate] numbers to match up" with people that have been rescued or confirmed dead or "in that gray area of folks we're worried about."
The governor also spoke about the emotional toll the tragedy has taken on rescue workers. Beebe said he met with families whose relatives had died.
"I visited with a young man whose wife we found today," he said. "That was pretty hard. I visited with a lady who had lost her children and husband."
He paused. "There's not much you can say in a situation like that."
Nick Hofert awoke just after 2 a.m. Friday to screams from families, some with children as young as 4, hurrying toward the higher ground on which his cabin stood. He ushered them into his home and then went outside to try to find those who had become separated from the group.
Despite the rising water, he and others found the missing relatives at an RV site.
At one point, Hofert thought the group would have to evacuate his cabin and climb farther up the mountain, but the threat eased as the rains subsided.
"The water was rising faster than I've ever seen," Hofert told CNN's Rick Sanchez. People "were coming from everywhere, like ants running from water."
Ginger Autrey awoke to a phone call notifying her that her teenage son and other relatives who had gone camping at the site were missing. There were reports the boy walked out off the riverbank, but there hasn't been any sign of him, she said.
"I just want my baby, I just want to see his little face," she told CNN affiliate KTHV-TV in Little Rock. "Nobody knows where he's at."
Video from the scene Friday showed a river coursing through the valley. The floodwaters tore asphalt, downed trees and crushed cabins.
The secluded campground has been frequented by generations of families who have returned to the cabins for decades, said Whitney Bettis, who was relieved to hear that her aunt and uncle survived.
"The way you measure things in Arkansas, I guess, is to the nearest Wal-Mart," Bettis said. The campground "is probably a good 45 minutes to an hour to the nearest, you know, sit-down restaurant or anything like that. It's a very beautiful part of the state."
"I can remember sitting on the edge of the river and playing with tadpoles and catching crawdads. ... I'm seeing the pictures of cabins that I remember from when I was 10 years old. This is really hard to watch."
Military helicopters are continuing to search the area while rescuers hunt by foot along at least 25 miles of river, Beebe said. Law enforcement, National Guard and parks personnel were working on search-and-rescue efforts.
Lincoln said she is praying for those injured or trapped and praised the first responders at the scene.
"As Arkansans, we have experienced our share of severe weather. Through it all, our citizens remain strong and resilient," she said in a statement.
President Obama instructed the Federal Emergency Management Agency to be in close contact with Arkansas emergency management officials and "to report back concerning any unmet needs."
"When natural disasters strike, our first responders are on the front lines providing emergency assistance and keeping our communities safe," Obama said in a statement. "Many of them are showing true bravery today and for that I thank them."
Janice McRae, whose property sits adjacent to the campground, said she and her husband woke in the middle of the night to a knock on the door from a cabin owner. The sight of flooding and destruction caught her by surprise.
"It was raining, but we didn't know that there was going to be flooding, because we hadn't had much rain lately," she said. "The ground wasn't wet, wasn't saturated. We weren't worried about it."
McRae said she and her husband rescued two boys they found stranded on the roof of a flooded cabin.
She described people clutching to trees in pitch darkness as cars floated past.
The county coroner said he was preparing for more possible deaths.