(RNN) - At least 15 tornadoes are confirmed to have touched down Wednesday in the Midwest, including one twister preliminarily rated an EF4 - the second most severe on the National Weather Service's scale - which killed six people in southern Illinois.
The storm that battered Harrisburg, IL, had winds estimated at 170 mph, moving at 60 mph. The sheriff's office said the tornado touched down at 5:56 a.m. ET, injuring 100, and damaging or destroying 250 to 300 houses and 25 businesses. Five of the six who were killed in Harrisburg were in the same apartment complex.
While many people are still missing, 13 are reported dead and at least 200 were injured in several states, CNN reported. In addition to the six deaths in Illinois, three people were killed in Missouri, three in Tennessee and one in Harveyville, KS.
In Harrisburg, tractor-trailers flipped over, power lines were torn down, mattresses hung from trees and windows and doors were blown out at businesses. Damage at Harrisburg Middle School led to the cancellation of classes for the rest of the week.
Harrisburg Medical Center was severely damaged, with its south wall succumbing to the winds around 10 a.m. ET.
"Going out - and again - after looking at the debris field and looking at everything in the darkness, it was horrifying, but even more so when the sun came up," Harrisburg Mayor Eric Gregg told CNN. "You got a picture and you got your hands around what the track of this terrible storm did to the city of Harrisburg. We just hope that we never have to experience anything like this again."
The Illinois tornado was part of a dangerous storm system that roared through the Ohio River Valley region and injured hundreds across several states, including Illinois, Missouri, Kentucky, Kansas, Nebraska, Indiana and Tennessee.
WSMV reports that three people have died in Tennessee after the same severe weather system moved through the state. Officials report two of those who were killed lived in Cumberland County. The third victim lived in DeKalb County.
Missouri took several hits from the storm, which produced 14 tornadoes between midnight and 4:30 a.m. ET, according to the NWS. Kentucky was hit by nine tornadoes while Illinois faced three and Indiana faced one.
The NWS is keeping a list of storm damage across the Midwest on its website.
In Buffalo, MO, a small town 35 miles north of Springfield, MO, one person was killed in a trailer park, and 13 people were injured.
The Associated Press reports another person was killed south of Springfield in Cassville, MO.
The storm continued east, slamming into downtown Branson, MO, at about 2 a.m. ET, cutting a 22 mile long path through the city, including the entertainment and theater district, according to the AP.
"The theater next to me kind of exploded. It went everywhere. The hotels on the two sides of me lost their roofs. Power lines are down. Windows are blown out," John Moore told the AP. "There's major, major destruction. There has to be millions dollars of damage all down the strip."
Branson Mayor Raeanne Presley told CNN that if the tornado had hit the town two weeks later, there may have been more injuries. The town's tourism season was ramping up and spring break travelers were headed to the town known for its country music venues and theaters.
The AP also reports that 32 people were treated in Branson's Skagg Regional Medical Center, mostly for cuts and bruises. No one was killed.
CNN reports that volunteers from Joplin, MO, are headed to Branson to help with cleanup. On May 22, 2011, an EF5 tornado destroyed Joplin, killing 160 people. Volunteers from all over the country and state - including Branson - flooded the town to help with recovery.
In Stoddard County, MO, Sheriff Cark Hefner told KFVS that several mobile homes were destroyed – displacing one about 200 feet - and two people were airlifted to a hospital in Cape Girardeau, MO, where one man died.
The storm then moved into the Ohio River Valley, with sightings of funnel clouds in Kentucky and reports of storm damage. Homes have been damaged in Madisonville, KY, according to WFIE.
The NWS confirmed a tornado had touched down in Hardin County near Elizabethtown in addition to more tornadoes in Grayson County and LaRue County, according to WAVE.
In Newburgh, IN, the historic downtown received some damage, but no one was injured.
The severe weather also took a swipe at northern Oklahoma, where trailers were flipped and a wall cloud was sighted; as well as hail in northern Arkansas, the AP reports.
Many states in the region also reported large hail and strong winds.
In the upper Midwest, snow and wintry conditions are blanketing cities in the Dakotas, Minnesota and Michigan.
The storms first took shape Tuesday when nine tornadoes touched down in Nebraska, Kansas and Missouri, according to the NWS.
One person succumbed to their injuries in Harveyville, KS, according to KCTV, where the powerful storms destroyed about half the town.
Emergency officials are assessing damage in Harveyville, KS, after an EF2 tornado plowed through around 9 p.m. Tuesday, injuring at least nine people. KCTV reports that numerous homes, a church and an apartment building were damaged.
The wreckage caused Kansas Gov. Sam Brownback to declare a State of Emergency for the town.
The mayor of Harveyville, Dustin Kuntz, is concerned the damage may not reach the amount needed to receive FEMA aid.
The threat of severe weather has not ended. While there are currently no tornado warnings in effect right now, watches have been issued through northern Alabama, northern Mississippi and southern parts of Tennessee until 10 p.m. ET.
The NWS predicts that severe weather – which includes the possibility of tornadoes – is expected over the some of same region on Friday, including the Ohio River Valley and Tennessee River Valley, as well as into southern states such as Mississippi and Alabama.
Copyright 2012 Raycom News Network. All rights reserved.