SHAWNEE, Oklahoma (CNN) — A powerful tornado blasted an area outside of Oklahoma City on Monday, ripping roofs off buildings, leveling homes and leaving a massive band of destruction in its wake.
In the desperate seconds and minutes after the storm passed, the human toll was yet to even begin to be counted.
Survivors emerged from shelters to see an apocalyptic vision -- the remnants of cars twisted and piled on each other to make what had been a parking lot look like a junk yard. Bright orange flames roaring from a structure that was blazing even as rain continued to fall.
At least one school was in the tornado's devastation zone in Moore, Oklahoma. Lance West, a reporter for CNN affiliate KFOR, says there were people pulling students from a classroom at an elementary school heavily damaged by the tornado. There were no immediate reports on the condition of the children.
"Our worst fears are becoming realized this afternoon," Bill Bunting, with the National Oceanic and Atmospheric Administration's Storm Prediction Center, told CNN.
"We certainly hope everyone heeded the warnings, but it's a populated area and we just fear that not everyone may have gotten the word," he said.
The tornado was estimated to be at least two miles wide at one point as it moved through Moore, KFOR reported.
More than 171,000 people could have been in the path of the storm.
Video from CNN affiliates KFOR and KOCO showed widespread destruction in the city of Moore, which is part of the Oklahoma City metropolitan area.
"It's just destroying everything. There's so many homes in the air right now. The motion on this storm is sickening," said storm chaser Spencer Basoco.
Bunting warned the worst may be yet to come.
"These storms are going to continue producing additional tornadoes. They'll also produce some very, very large hail, perhaps larger than the size of baseballs. We're also concerned that there may be an enhanced and widespread damaging wind threat with storms as they merge together," he said.
"As bad as today is, this is not over yet."
Moore Medical Center in Oklahoma was evacuated after it sustained damage, a hospital spokeswoman said.
All patients were being evacuated to Norman Regional Hospital and Health Plex Hospital, and residents injured in the storm were being told to go to those centers as well.
The severe weather came after tornadoes and powerful storms ripped through Oklahoma and the Midwest earlier Monday and on Sunday.
Earlier, forecasters had warned that the destructive weather, which killed at least two people, was perhaps just a preview of things to come.
"Today could be potentially as dangerous as yesterday," CNN meteorologist Indra Petersons said Monday morning, pointing to a wide swath of the country spanning from Texas to Michigan. "We're talking about 500,000 square miles under the gun for severe weather."
Even before Monday afternoon's devastation, residents in areas hard hit by weekend storms were combing through rubble where their homes once stood.
"My mind is, like, blown, completely blown," said Jessie Addington, 21, who found that few pieces of her childhood home in Shawnee, Oklahoma, were still standing Monday.
Addington, who now lives in a nearby town, said her mother huddled in the mobile home's bathroom when the weekend storm hit. But the tornado still tossed her around like a rag doll, leaving her bruised and battered.
When Addington arrived, she was shocked to find the neighborhood where she had lived for 17 years reduced to ruins.
"I'm feeling cheated, to be honest," she said, "like, it's just all gone."
An estimated 300 homes were damaged or destroyed across Oklahoma in weekend weather, Red Cross spokesman Ken Garcia said.
Viewed from the air, the extent of the damage was staggering, said John Welsh, a helicopter pilot for CNN affiliate KFOR in Oklahoma. "Like you took the house, you put it in a gigantic blender, you turned it on pulse for a couple minutes and then you just dumped it out."
And that was before the monster tornado moved in Monday afternoon.
Oklahoma resident: 'It's just devastating'
Two men, both in their 70s, were confirmed dead as a result of an earlier tornado that hit Shawnee, said Amy Elliott, a spokeswoman for the state medical examiner's office.
When Kimberly Graham returned to the spot near Shawnee where her mobile home once stood, her 7-year-old son's orange bicycle was one of the only items that remained.
"Home, cars, garage, everything -- gone," she told CNN on Monday. "It's just devastating. Everything that you've worked for. Everything that you've built."
As many as 28 tornadoes were reported in Oklahoma, Kansas, Illinois and Iowa, according to the National Weather Service, with Oklahoma and Kansas the hardest hit. Some of those reports might have been of the same tornado.
More tornadoes were spotted in Iowa, near Earlham, Huxley and east of Dallas Center, according to the National Weather Service.
The agency also confirmed a twister in the northwestern Illinois county of Carroll.
A combination of factors -- including strong winds and warm, moist air banging against dry air -- means severe weather could continue sweeping across a wide swath of the United States for days, Petersons said.
"Keep in mind we have all the ingredients out there that we need," she said.
Tornado watches were in effect for portions of southeastern Kansas, western and central Missouri, northwest Arkansas, central and eastern Oklahoma and northwestern Texas until 10 p.m. (11 p.m. ET).