UPDATED 03/01/12 5:37 a.m.

HARRISBURG, Ill. (CBS) — Six downstate residents were killed, and more than 100 others were injured, in a powerful storm with an EF4 tornado slammed southern Illinois early Wednesday.

READ MORE: Aldermen To Vote On $14 Million Settlement In Wrongful Conviction Case In 1989 Murder Of Retired CPD Sergeant's Wife

Gov. Pat Quinn has declared a state of emergency in Harrisburg, Ill., which sustained the most serious damage, killing four men and two women.

Quinn also joined Lt. Gov. Sheila Simon, a native of nearby Carbondale, in meeting victims of the tornado and viewing the damage on Wednesday.

“I just toured the area, I saw how devastating the damage is; the overturned semis, and cars, and apartment buildings shredded to bits. It’s very, very important that we understand anytime this bad thing happens from nature, that we don’t give up; that we help those who have been devastated by this natural disaster,” Quinn said.

“It’s devastating. If you go to the homes, many people have lost their entire house, the roof of their house. The commercial damage here, it’s completely obliterated,” Quinn told CBS 2’s Mike Puccinelli Wednesday evening, while standing near a strip mall that was destroyed by the tornado.

The governor noted that it was lucky the tornado struck a commercial area of Harrisburg at the time it did. Since it hit early in the morning, the businesses were likely empty, while they would have been full of employees and customers if the storm hit midday.

“We lost six people. We should pray for their immortal souls and mourn their loss,” Quinn said. “But the property damage is a mess and we have to calculate it all.”

In addition to declaring Harrisburg a state disaster area, Quinn said he hopes to get federal aid by getting President Barack Obama to declare Harrisburg a federal disaster area.

The storm produced an EF4 tornado, according to the National Weather Service. CBS affiliate KFVS reported the peak wind during the storm clocked in at 180 mph.

The strongest category of tornado is an EF5.

The Saline County Sheriff’s office says 100 people were injured in and around Harrisburg during the storm, and at least 300 houses and 25 businesses were damaged or destroyed.

Puccinelli reports the town of about 9,000 people had about 250 to 300 homes severely damaged by the tornado.

A strip mall in Harrisburg that had been demolished.

In a bathroom in what had been a Game Stop store in the strip mall, cleaning supplies remained on the shelf and the toilet remained anchored to the floor. But the exterior walls had left the bathroom exposed to the outside.

Beyond the bathroom, some parts of the roof were hanging precariously, while others had been knocked flat. Insulation was on the ground, and walls were teetering.

And much of the mall was obliterated altogether when the storm came in at 4:56 a.m. Wednesday.

The fact that the tornado hit before sunrise actually prevented what could have been a far deadlier situation.

READ MORE: Art Institute's 'A Sunday On La Grande Jatte' To Be Displayed Reframed On Tuesday

“Had this been at 10 o’clock in the morning, when people were shopping and just doing what they normally do, I think the damage and the death toll could have been much higher,” said Illinois Emergency Management Agency director Jonathon Monken.

Harrisburg resident Larry Volle saw people being taken from his neighborhood – some conscious, some not.

“They were bringing a lot of people up out of there this morning,” Volle said. As to whether they made it, he said: “Well, we don’t know. They were on stretchers.”

Volle was in a house with Kelly Ratliff and her daughter, Jessica, when the storm hit.

“It was terrifying. I’ve never been through anything like this,” Ratliff said. “It did sound like a train coming through the living room.”

The local hospital, Harrisburg Medical Center, was also hit hard by the twister. One wall of the hospital was taken out by the storm.

Patients at the hospital had been moved before the storm hit, but hospital workers said it was a horrific experience.

“It was right about quarter to 5, when I really couldn’t hear the tornadoes so much as I heard the explosion when the windows blew out and the wall came out,” said Jane Harper. “There was this white, gray kind of mist that … rained down from the ceiling. We started getting water. All the fire alarms went off. The power went out and all the electric doors closed, and it was total chaos for a while.”

One young man, Lucas Gurley, lost his lifelong friend, Jaylynn Ferrell, to the tornado.

“She was just the smartest girl, real friendly, always had a smile on her face – just a great all-around person, really,” he said.

Gurley said he had known the nursing student since kindergarten.

Power lines in Harrisburg have been ripped down, gas lines are leaking, and streets are blocked, KFVS reported. Sightseers are being asked to stay away from Harrisburg.

“It’s a horrific event that’s happened to us here in Harrisburg – you know, the loss of life, the injureis and the devastation – it’s just profound and it’s heartbreaking,” said Harrisburg Mayor Eric Gregg.

But Gregg is vowing to rebuild.

“We will rebuild this city. We will make this city stronger,” Gregg said. “This will not stop us.”

LISTEN: WBBM Newsradio’s John Cody reports

Classes at Harrisburg schools were canceled. Harrisburg Middle School also sustained damage, KFVS reported.

MORE NEWS: New Shield Testing Site Now Available At DePaul University's Loop Campus

(TM and © Copyright 2012 CBS Radio Inc. and its relevant subsidiaries. CBS Radio and EYE Logo TM and Copyright 2012 CBS Broadcasting Inc. Used under license. All Rights Reserved. This material may not be published, broadcast, rewritten or redistributed. The Associated Press contributed to this report.)