By Brandon Merano, Jermont Terry, and Mugo Odigwe

ROCKTON, Ill. (CBS) — Authorities are allowing a massive chemical plant fire in Rockton, Illinois, burn itself out, which could take several days, rather than risk chemical runoff spilling into the nearby Rock River.

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The fire has prompted Gov. JB Pritzker to send in the Illinois National Guard.

The fire began around 7 a.m. Monday at the Chemtool plant at 1165 Prairie Hill Rd. Some neighbors in the area reported hearing small explosions as the fire started burning. The company manufactures fluids, lubricants, and grease products for machinery.

On Tuesday, officials said barriers are currently being put in the river for protection and fire crews will begin utilizing foam on the blaze. Fire suppression operations will continue throughout the day.

Rockton police confirmed, Tuesday, monitoring devices have been set up around the area. Good ground-quality air has been detected and no contaminants have been reported. Water contamination monitoring is ongoing and officials will continue to provide updates.

Anyone within a three-mile radius is asked to still wear masks for lung protection, and residents in the one-mile evacuation zone need to remain out of the area Tuesday.

Public health officials will answer any community question through a new hotline at 815-972-7300 or by email at rocktonchemfire@wchd.org.

Police also confirmed on Tuesday that two people injured in the fire, including a firefighter, have been treated and released from local hospitals.

Officials said the fire is likely to burn for at least seven more days. The investigation by state and federal agencies remains ongoing Tuesday.

Fire department officials said Monday the air near the plant is safe at ground level, and all workers at the factory were safe. The fire prompted a mandatory evacuation order near the plant.

CBS 2’s Brandon Merano reported, Monday night, he could see the plume of smoke from the fire from 50 miles away as he headed to the scene.

“It literally looked like we had a volcano going off, and the smoke was so intense,” said area resident Ryan Chester.

More than 40 fire departments were called in to help contain the fire, fighting falling debris and grass fires in nearby yards.

“The debris falling down — we had a few ashes and stuff come down in the street, but nothing like what we saw coming down in the neighborhoods behind Chemtool,” Chester said. “It’s just massive. It’s insane.”

Rockton Police said the Rockton Fire Protection District has ordered a mandatory evacuation for all homes and businesses within one mile of the factory. As of late Monday night, a total of 1,500 people living within five blocks of the plant had been evacuated from their homes.

As CBS 2’s Jermont Terry reported, emergency crews had to monitor overnight to ensure that others were not in immediate danger with darkness.

Residents were advised to proceed to either Stephen Mack Middle School or Roscoe Middle School. The Salvation Army and Red Cross were on standby at the school sites.

Others said they would rent a hotel room for the night or stay with family.

Winnebago County Public Health Administrator Dr. Sandra Martell also said anyone within three miles of the fire should wear a face mask when outdoors.

Meanwhile, Rockton Fire Chief Kirk Wilson said crews are letting the fire burn itself out, rather than pouring any more water on it, out of concern about chemical runoff into the nearby Rock River. Wilson said it could take a matter of days for the fire to completely burn itself out.

“That’s the best thing that we can do right now,” Wilson said. “The main thing is that we don’t want an environmental nightmare to occur, and the reason that we would cause that is by the use of water streams. So we stopped water operations at this point.”

Wilson said crews also have been conducting air quality tests, and have determined there is no danger to air quality at ground level.

“I assure you that there is no danger at ground level at the plant, but just for a precautionary measure, we decided that it was in the best interests of community safety that we evacuated the area,” he said.

Wilson said the fire was already burning through the roof of the plant when the first crews arrived, and at that point there was no stopping it. He said the plant already has been “pretty much consumed” by the fire.

“This was a fast-moving fire. It was wind-driven,” he said.

CBS 2 meteorologist Laura Bannon reports the massive smoke plume from the fire is even visible on weather radar. The smoke could be seen as far away as Kankakee, more than 100 miles away.

As the smoke continued billowing from the burnt up chemical plant, crews on the ground were busy putting out grass fires and working to make sure the fire did not spread.

“I want to make sure the firefighters that were working on scene were safe as well,” Wilson said.

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Wilson said all 70 employees who were working at the plant at the time were safely evacuated. No workers were hurt, but one firefighter suffered a minor injury.

On Monday afternoon, Gov. Pritzker activated the State Emergency Operation Center to respond to the fire. The response included members of the Illinois National Guard, who headed to the scene in mobile response vehicles.

The Illinois Environmental Protection Agency and the Illinois Emergency Management Agency have also sent crews to the area.

“I am monitoring this situation closely and will make all resources available to the surrounding communities as we work to keep people safe,” Gov. Pritzker said in a news release. “Teams from multiple state agencies are on the ground and coordinating closely with local authorities and we will continue to make additional information available as soon we have it. To those impacted, please listen to guidance from emergency officials and know that the state of Illinois is doing everything possible to protect you and your loved ones.”

Illinois EPA Director John Kim said the agency will be monitoring as the fire burns, and will also ensure that hazardous conditions are properly addressed once the fire is out.

Kim said the greatest concern late Monday was the dangerous chemicals that Chemtool uses. The plant is one of the largest of its kind in the country using substances such as antifreeze, sulfuric acid, lead, and nitrogen.

Wilson said the U.S. Environmental Protection Agency was also on the scene.

Rockford Fire Department Division Chief of Operations Michele Pankow said the City of Rockford and other agencies also activated the Winnebago County Emergency Operations Center to fight the fire.

The explosions and fire left many alarmed. Lindsey Oswald, of nearby South Beloit, was getting her family ready for the day, when she heard the explosions and left.

“We heard a bunch of sirens, and then we opened up our sliding glass door above the river, and you could just hear explosion after explosion after explosion. And then just all the black smoke coming in across the back of our house. So I grabbed my husband. He had just gotten out of the shower and ready for work. My girls and I were just getting ready to start our day, and he went outside and saw it, and we all just got out of the house as soon as possible,” she said. “We left without our animals. Luckily, one of our neighbors, when they formally evacuated, he was able to get back in our house and grab our dog, and get him to the boarders for us until we get our bearings and figure out what we’re doing.”

A Red Cross disaster team has been deployed to the area to help people forced to evacuate their homes.

“Hoping that everybody across the street was safe. Hoping that a million jobs aren’t wrecked in the recovery of this whole entire thing,” Oswald said. “There’s a million things different, you know, go through your head.”

Eric Ross also woke Monday to find a plume of smoke in the air.

“I thought it was a black cloud for the moment, but there was blue surrounding it,” he said. “And I’m like, a split second later, I knew that it was a fire.”

Fifteen whole hours later, Ross and his family were still watching what was in the air over their home.

“We don’t know what was there. We don’t know where it’s going,” Ross said. “I know that there’s debris, and you know, anything that’s blowing in the air could be a concern.”

Chemtool employs 125 people at the Rockton plant, which has been hit with two different occupational safety and health administration complaints – one in 2013 and the other just last month. The investigation not the latter complaint remained under way as of Monday.

“They are a huge employer in town and it’s going to affect a lot of families,” said Chief Wilson. “It will be devastating.”

The company has confirmed all of their workers are safe and accounted for. They do not yet know what caused the explosion and fire, and have deployed a risk management team to determine the cause.

And as more than 40 agencies fight to contain the raging fire, the realization of loss resonates with residents such as Oswald.

“Praying for all the businesses and families on that side of the river and in the Rockton community,” she said. “It’s heartbreaking. You get to know these people really well throughout your life, so it’s just a lot to take in a day.”

Chester praised the quick action from first responders and the community impulse to come together.

“The quick response from all the communities and fire departments from all over the state and Wisconsin have been tremendous,” he said. “It’s been awesome to see the community rally together behind people who have been displaced or those workers at Chemtool.”

When she learned the fire could go on burning for several days, area resident Michelle Taormino said: “We’ll that’s a little concerning. If anything changes, we have lots of safe places to go.”

As the sun set, crews must monitor closely the wind directions overnight. The darkness makes it harder to see where the smoke is blowing.

Ross’ home is just under two miles away. They have been advised to wear masks, but they are hoping they don’t get a knock in the middle of the night.

“Hell yeah, I think it would be a little different once the black cloud comes over to get us,” Eric Ross said.

Wilson said late Monday that he did not know when evacuated residents would be allowed to return home. He said air quality checks were under way in Rockton and nearby Roscoe.

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Investigators late Monday were still trying to determine what caused the explosion.

CBS 2 Chicago Staff