More than 25 years ago, a rash of deaths among tornado victims trapped in cars in Wichita Falls, Texas, led to what is now a basic tenet of storm safety: When a twister is on the horizon, stay out of your car.

Authorities are echoing that same warning after a weekend tornado devastated several rural communities in southwest Missouri and across the state line in northeast Oklahoma.

Eight of the 23 victims in the two states died in cars, troubling experts who say the inside of a vehicle is one of the worst places to be during a twister.

“It’s like taking a handful of Matchbox cars and rolling them across the kitchen floor,” Sgt. Dan Bracker of the Missouri State Highway Patrol said, surveying the damage in and around Seneca, near the Oklahoma line. “This is devastating.”

At least 26 people died in Missouri, Oklahoma, Georgia and Alabama when severe storms erupted Saturday over the Southern Plains and swept eastward. Sixteen people died in Missouri from the same storm that ravaged Picher, Okla., a town 32 miles away where seven were killed.

Officials from the Federal Emergency Management Agency, which determines whether residents qualify for federal assistance, were in both states. FEMA Director David Paulison and Homeland Security Secretary Michael Chertoff were scheduled to visit the hardest hit areas on Tuesday.

Scientists from the Environmental Protection Agency arrived in Oklahoma on Monday to check for high lead levels in Picher, a heavily polluted former mining town where lead-filled waste is piled into giant mounds.

Miles Tolbert, Oklahoma’s secretary of the environment, said he did not believe there was any immediate hazard to the 800 residents. But he said more testing was needed.

Among those killed were three people in Oklahoma who were rushing to reach a relative’s house in their car; a woman whose car was blown off a road near Seneca; and four family members _ Rick Rountree, his wife, his 13-year-old son, and his 76-year-old mother-in-law _ who were in a van on the way to a friend’s wedding when a twister with winds of 170 mph struck the Seneca area on Saturday.

“They were on the road when the warnings came,” said Rountree’s brother-in-law, Larry Bilke.

Two people were killed in Georgia, where meteorologists said at least six tornadoes touched down. One struck McIntosh County’s emergency management center, destroying the fire trucks and ambulances inside. Another man was killed in northern Alabama when his truck was struck by a falling tree limb as he was surveying storm damage.

According to data from the National Weather Service’s Storm Prediction Center, 49 of the 705 deaths _ or about 7 percent _ attributed to tornadoes from 1997 to 2007 were people who were in vehicles when the storm struck.

“They can cover more ground than you can in your car, so unless you know you are moving away from the tornado the best thing you can do is find a strong structure,” said Andy Foster, a meteorologist with the National Weather Service.

The twister that struck Seneca and surrounding Newton County was moving at 50 mph to 60 mph, Foster said. One car was found a half-mile from the tornado track.

In Newton County alone, 200 people were treated for injuries at hospitals, 200 buildings were destroyed and another 200 structures suffered major damage, said Gary Roark, the county emergency management director.

Authorities were still piecing together how some of the other victims died over the weekend. But the Missouri Highway Patrol said one person was killed when her vehicle was blown off the same road where the Rountree family died.

In Picher, a man and a woman died when their car was blown into a lagoon. The body of another man from the car wound up in a nearby tree. A 13-year-old girl who was riding in the car was injured.

Fire Chief Jeff Reeves said they were not trying to outrun the twister.

“I think they were actually trying to get to a family member’s house on the south side of town to help them and they just didn’t make it over,” Reeves said.

Cars have the same problem as mobile homes in a storm: they aren’t anchored to the ground, so winds can get underneath them. Winds of less than 100 mph can flip a car, said Rick Smith, warning coordination meteorologist with the weather service.

The motorist deaths prompted Missouri Gov. Matt Blunt to issue a stern reminder to people to stay out of cars in storms.

Officials say drivers and their passengers should find a sturdy shelter or even lie flat in a ditch or other low spot, covering their heads with arms, coats or blankets if a tornado is moving in their direction.

Overpasses and bridges should also be avoided _ overpasses can create a wind-tunnel effect, and bridges can collapse.

After touring the damage Monday by helicopter and on foot, Blunt called the weather-related destruction “some of the worst I’ve seen.”

The National Weather Service said about 100 people have died in U.S. twisters this year. This could become one of the deadliest tornado years in recent history.

The weather service’s Storm Prediction Center in Norman, Okla., said 130 people died in U.S. tornadoes in 1998, the eighth deadliest year since 1950. The highest number of tornado-related deaths came in 1953, when 519 people died.

To date this year, 910 tornadoes have been reported, though not all have been confirmed by the weather service. That compares with 1,093 confirmed twisters for all of last year.

Harold Brooks of the National Severe Storms Laboratory said the highest number of tornadoes ever recorded through May 11 of any year was 676 in 1999. Brooks said he expects the number of confirmed tornadoes through mid-May of this year to end up in the 650-to-700 range.

Tornado season typically peaks in the spring and early summer, then again in the late fall.

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Associated Press writer Murray Evans in Picher, Okla., contributed to this report.