(CNN) -- Rescue crews scoured Oklahoma river banks Monday for six people who remained missing after last week's tornadoes.
At least 17 people died in the storm, authorities said Monday. Three more people were reported dead Monday. They died Saturday in separate drowning incidents, according to the department of public safety and the sheriff's office in Oklahoma County.
Among the dead were five children, including three who died along with two adults swept away by rains after hiding from the tornado in a storm drain.
In eastern Oklahoma County, a 66-year-old man on his way to work was killed in the early morning hours Saturday when he drove off a washed out bridge and drowned in a creek.
Seven Guatemalan citizens are known to have died in the storm, according to the country's Consulate General in Houston. Four Guatemalan citizens were missing, the consulate said. It was not immediately clear whether the dead and missing were part of earlier tallies provided by Oklahoma officials.
Three others who died were storm chasers: Timothy Samaras, his son Paul and Carl Young.
The fate of the six missing remains uncertain. Rescue crews will search until dusk Monday, Oklahoma Deputy Fire Chief Marc Woolard said.
And the damage wasn't confined to Oklahoma. In Missouri, a twister left more than 10 miles of significant damage "that caused dozens and dozens of houses to be literally blown up," Gov. Jay Nixon told CNN affiliate KSDK.
No one was killed in that tornado, but three people drowned in Missouri, Nixon said.
A five-mile stretch of the Mississippi River near the Port of St. Louis was shut Monday to smaller boats.
And in Arkansas, flooding killed at least four people: a sheriff's deputy, a wildlife officer and two women they were trying to save from a deluged home.
'Memories just tossed about'
But it was Oklahoma City and its surrounding areas that sustained most of the damage.
The storm system mowed down power lines and uprooted trees, flipped big rigs on their sides and ripped off part of the terminal roof at Oklahoma City's Will Rogers World Airport, where some 1,500 area residents had taken shelter in a tunnel.
The twisters tore open brick houses like cartons, sucking out their contents and tossing them out onto lawns.
"It's a sombering thing to think about life and to see all your memories just tossed about," Kris Merritt said as he surveyed the damage at his parents' house. "Everything from your childhood on up."
Though Friday's tornadoes were not as strong as the EF-5 twister that killed 24 people on May 20, fear drove some people to flee in cars, ignoring warnings not to drive.
Some drove on the wrong side of the highway. Interstates turned into parking lots.
'We were floating'
One tornado swept up a truck carrying a crew from The Weather Channel, hurled it 200 yards into a field and smashed it to the ground.
"I saw people in my life, I saw their faces flash right in front of me," meteorologist Mike Bettes told CNN on Sunday. "And it just seemed for a moment, everything was in slow motion, especially when we were floating."
The crew members were lucky. They survived.
But the storm did claim the lives of three other storm chasers.
The Samarases and Young were killed while chasing a tornado in El Reno.
At the intersection where authorities believe the men were killed, crews hauled away a mangled white truck that had been crushed like a tin can. The metal frame of their storm-chasing vehicle was twisted almost beyond recognition.
"A vehicle is not a place to be in any tornado," CNN meteorologist Chad Myers said. "Especially a big one like that, and those men doing their job, those field scientists out there doing their jobs, were killed in the process."
Storm chaser Reed Timmer, who knew Samaras well, said Monday he was "astonished" by what had happened. Samaras had a well-earned reputation for safety, he said on CNN's "Starting Point."
"I just don't understand," he said. "Something must have gone wrong, horribly wrong."
'We were overwhelmed'
Once the tornadoes passed, Oklahomans faced a new threat: floods.
Eight to 11 inches of rain hosed Oklahoma City, stranding motorists and hitting apartments in low-lying areas of town hard.
"We saw flooding in areas that we don't see flooding," said police Lt. Jay Barnett. "We were overwhelmed."
The flash flooding swept some bodies up to 5 miles downstream, Oklahoma City Deputy Fire Chief Marc Woodard said.
Among those killed were Samuel Cifuentes, his wife, Florinda Santos, and their 5-year-old son, Alex Cifuentes, Samuel's brother told CNN.
Authorities had been searching for the family members in a storm drain.