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A response to a fire at a chemical plant in Georgia on Sunday morning forced evacuations and road closures in the area, according to Rockdale County officials.

The fire broke out around 5 a.m. ET on the roof of the BioLab in Conyers, Georgia. Water from a sprinkler head that officials had previously described as defective “came into contact with a water-reactive chemical and created a cloud,” district officials said on their website.

CNN has reached out to BioLab, which makes pool and spa treatment products, for comment.

A fire broke out on the roof and firefighters were able to contain the blaze, but it reignited hours later, Rockdale County Sheriff Eric Levett said in a video message posted on Facebook.

The fire was extinguished around 4 p.m. ET, Rockdale County Fire and Rescue Chief Marian McDaniel said, but the cloud of the chemical reaction can still be seen for miles and is causing problems for residents. The smoke could be visible for several days, she added.

The cause of the fire and the chemicals involved remain unknown, McDaniel said.

“I would urge all of you to spread the word to stay away from this area at this time,” Levett said. “It burns pretty well. We’re trying to get that under control, but at the same time we’re also trying to get the traffic under control.”

Roads in the area are closed and residents between Sigman Road and Interstate 20 have been ordered to evacuate – about 17,000 people, according to Sharon Webb, director of the county's emergency management agency. Additionally, the highway is closed in both directions between Salem Road and Turner Hill. The sheriff said he would request assistance from the Georgia Department of Public Safety and the Georgia State Patrol.

Residents north of Sigman were asked to shelter in place and keep their windows closed.

Conyers Mayor Vince Evans urged residents who decide not to evacuate to stay put and not hike or drive around town.

“This is not the time for any kind of sightseeing. We strongly encourage everyone, no matter where you are from, but especially Rockdale residents, to stay away from this area,” Levett added.

At around 7:45 p.m., officials asked all county residents to shelter in place until midnight.

A local hospital began transferring patients to other facilities as a precaution, and officials asked those with an urgent medical emergency to go to an area hospital or one in another county, Webb said.

Rockdale County Executive Oz Nesbitt told CNN's Jessica Dean it was an “all hands on deck” situation.

“All of our resources have been deployed and deployed,” Nesbitt said. “Every agency available, GEMA, FEMA, everyone is on deck here in Rockdale County, we are managing this situation and trying to get it under control.”

Environmentalists are conducting air quality tests to determine whether the smoke contains toxins.

“We are not taking any risks,” the chairman added.

The roof of the chemical plant building has now collapsed and Nesbitt described the damage as a “complete collapse.”

Residents of neighboring Newton County also received an alert Sunday about the situation in Conyers.

“We are monitoring the situation and advise that if you smell chlorine, turn off your air conditioning units, turn on your ceiling fans and, if possible, bring your outdoor animals indoors,” the message said. “If you have trouble breathing or another medical emergency, call 911. At the moment, sheltering in place is the best option.”

In September 2020, BioLab experienced a “thermal decomposition event” that also resulted in a fire that temporarily closed Interstate 20.

In its final report on the incident, the U.S. Chemical Safety Board noted that high winds from Hurricane Laura damaged the laboratory's warehouse and allowed rainwater to enter the building. The water came into contact with a chemical and triggered a reaction that caused the fire.

Conyers is about 30 miles east of Atlanta.

This is a developing story and will be updated.