Update: 4 p.m.
Cottleville fire crews say the chemical cloud threat has been mitigated and they are now leaving the scene. Highway 94 should re-open shortly.
Our original story:
There's a hazmat situation in St. Charles County at a water treatment plant off of Highway 94. The unintentional mixing of chemicals resulted in a cloud of hydrogen fluoride gas.
Cottlevittle Fire Chief Skip Stephens tells KMOX four people have been taken to the hospital. He says at the time of departure, two of the injuries were considered life-threatening and two were not.
"What we know about this chemical is that the onset of symptoms can be delayed and can worsen over time. So the [latest] condition of those four individuals, who were all adults by the way, is unknown at this time," he said.
There are road closures. These include: Highway 94 from D to Highway 40, DD at 94 is blocked, and 94 south of D is shut-down. People in the area are being told to stay in their homes.
"I would say 'stay out of the area,' but quite honestly you can't get into the area" because of the roads that are closed, he said.
Chief Stephens says the hazardous materials team is trying to go into the scene now to mitigate the gas cloud.