"The biggest hazard we have is the smoke and fumes as well as the gas from the fire. Highly poisonous and very deadly," said Chief Tracey Steffes, Morris Fire Protection & Ambulance District.
WATCH: Fire officials give update on Morris industrial fire
The blaze started at the old Federal Paper Board facility in the 900-block of East Benton Street. Inside, up to 200,000 pounds of lithium batteries set off large explosions.
"These batteries range in size of a cell phone to a little bigger than a car battery. As they get wet, they short out and they ignite and explode. That is the problem we are having," Steffes said.
Fire officials said that due to the nature of the fire, they are going to have to let it burn out on its own. That process is expected to take until at least Wednesday.
Crews had no idea the batteries were there, but once they found out, it changed the response. Firefighters weren't able to use water for fear the batteries would erupt, and foam was not an option either.
Tuesday's fire came less than one month after the massive blaze at the Chemtool grease plant in Rockton. Special resources still in the area from that fire are now being utilized in Morris.
"I do not know how you just store that many batteries and have no one know about it," said Alex Brachle, one of many in the area who evacuated. "I was at home and they knocked and said, 'You guys have to get out.'"
Officials evacuated the southeast side of Morris, bounded by Route 47 to the west, the railroad tracks to the north, the river to the south and Washington Street as far east as Evergreen Cemetery.
The evacuation is mandatory and expected to conclude at 9 p.m. on Wednesday, June 30, though officials warn that the conditions could warrant an extension.
Wes Garriott grabbed a few items and headed to the shelter. The 86-year-old is not sure when he can return home.
"I got my meds and stuff and the decision was real fast," he said.
The Grundy County Sheriff's Office said they are assisting with the response and the evacuations. If you need a place to go, they are using the Grundy County Administration Building at 1320 Union Street as a reception area.
If you smell or see the smoke, officials are asking that residents self-evacuate and then report where you saw or smelled the smoke.
Residents wanting to report smoke, or smell, ask questions about shelter or the evacuation instructions may call 815-941-3408.
"We are going to be here for the long haul," Steffes said.
The Red Cross is supplying food and water to the more than 300 first responders battling the fire. Red Cross volunteers are also working to set up a reception center and shelter for those who have been evacuated at First Christian Church, 455 W. Southmor Road, in Morris.
Governor JB Pritzker said he is sending Illinois National Guard troops to help at the scene.
So far, no injuries have been reported.