Clouds billow from the Wacker polysilicon chemical plant after an explosion released a hydrogen chemical gas on Thursday, Sept. 7, 2017, in Charleston, Tenn. The explosion closed the plant, but a statement from Wacker says air quality was unaffected.

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Explosion at Wacker is second incident within 8 days

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UPDATE: All Bradley County schools will be closed on Friday, Sept. 8 as a precautionary measure, according to a release from the Bradley County Sheriff's Office.

The release also states that the visible vapor cloud was only steam, and that advisories were given as precautionary measures.

A total of eight people were treated for symptoms related to the incident.

UPDATE: Officials said over radio that the cloud appeared to be steam, and air quality being tested by Wacker is at a safe level at this time.

Roads will remain closed for another 30 minutes before they consider reopening, the official said.

A Wacker firefighter has also been transported to a local hospital for heat exhaustion, according to James Bradford, the director of public relations for the Bradley County Sheriff's Office.

UPDATE: A shift in winds has caused Lauderdale Memorial Highway to be closed between Highway 11 and Interstate 75.

Neighbors within a one-and-a-half-mile radius to south of Wacker are urged to stay inside and turn off HVAC units until notified.

Emergency personnel said over radio that Exit 27 of I-75 is closed. Tennessee Highway Patrol and other first-responders, including a hazmat team, is being staged near Mouse Creek Road in Cleveland, Tenn.

Lauderdale Highway is also closed from Highway 11 to I-75.

UPDATE: The "Shelter in Place" advisory for Charleston residents has been lifted by the Bradley County Emergency Management Agency, according to a news release from the Bradley County Sheriff's Office.

Wacker Polysilicon is currently investigating the incident, which has left one person in the care of medical personnel.

UPDATE: According to a statement from Wacker, a mechanical incident resulted in a hydrogen chemical release. Wacker's immediate emergency response to contain the release resulted in a visible steam cloud. 

"Wacker is continuously monitoring air quality and measurements confirm air quality is not harmful. All Wacker employees and contractor employees are accounted for. The plant is temporarily closed. In accordance with Wacker's standard protocol the plant's incident response team immediately dispatched and was joined by Cleveland-Bradley County Emergency Management Agency." 

Interstate 75 is about to be reopened, emergency authorities said at 5:35 p.m. The interstate was shut down at exit 27 on the northbound side and exit 36 on the southbound.

Old Lower River Road along the Hiwassee River also just reopened.

One person is being taken out of the plant area by ambulance with cardiac-related problems, emergency responders said. 

The 38-year-old man has a history of cardiac problems but also was near the explosion and had first- and second-degree burns on his neck, an emergency responder said over the radio.

I-75 shut down at exits 27 northbound and 36 southbound. 

All traffic is being diverted off the interstate by the Tennessee Highway Patrol at those exits.

Jennifer Flynn, spokeswoman for the Tennessee Department of Transportation, said she didn't immediately know which alternate routes drivers will be told to use. 

Bradley County Schools released a statement on the explosion at Wacker:

Due to emergency personnel responding to Wacker, students from Charleston Elementary School and Walker Valley High School that were still in route home on buses were redirected to Ocoee Middle School.  Parents may pick students up there.  The buses are 1, 3, 22 and 43.  All students are safe. 

Any students or adults still at Charleston or Walker Valley are sheltering in place at this time. 

Residents in Charleston, Tenn., are being advised to shelter in place or to evacuate if they can safely leave. 

Bradley authorities are driving the streets of Charleston using loudspeakers to alert residents to the emergency.

One parent, Robyn Monroe, was in the area when the explosion happened and she said "you could feel it inside your bones."

"We can smell something in the aid and have a strange taste in our mouths...pretty scary," Monroe said in a Facebook post.

"It was kind of a puckery (sic) cottony taste. And the smell was that of stinky feet. I am assuming that was the hydrochloric acid." 

The $2.5 billion plant manufactures hyperpure polysilicon used in the manufacturing of solar panels. Work is underway now on a $150 million expansion.

ORIGINAL STORY: People in the area of Wacker Polysilicon are being urged to shelter in place after an explosion and chemical release just moments ago.

Authorities are saying a hydrochloric acid cloud was released. Emergency responders are shutting off access from Interstate 75 to Lauderdale Highway and U.S. 11 in Charleston, as well as exit 27. Dispatchers have ordered all emergency responders except the fire department to assemble on Lauderdale Highway north of the plant, and emergency management authorities are calling for respirators to be brought for responders on the scene.

"Get in a car, get inside, something," a Bradley County officer said via radio.

Bradley County Emergency Management confirmed an explosion at the plant and said it was being contained by the on-site fire department. 

A telephone caller who claimed to be a plant employee said there was a small explosion in the hydrogen recover building, then a larger blast. That information could not be immediately confirmed.

Bill Toth, director of corporate communications with Wacker's headquarters in Michigan, said the company is still gathering information on what happened and will release more information later.

Multiple emergency agencies are heading to the scene, the emergency management agency said. 

This is a developing story.

Stay with the Times Free Press for updates.