CONYERS, Ga. (AP) — Some residents east of Atlanta were evacuated while others were told to shelter in place to avoid contact with a chemical plume after a fire at a chemical plant.

Rockdale County Fire Chief Marian McDaniel told reporters that a sprinkler head malfunctioned around 5 a.m. Sunday at the BioLab plant in Conyers. That caused water to mix with a water-reactive chemical, which produced a plume of chemicals. The chief said she wasn’t sure what chemicals were included.

A small roof fire was initially contained, but reignited Sunday afternoon, Sheriff Eric Levett said in a video posted on Facebook as gray smoke billowed into the sky behind him. He said authorities were trying to get the fire under control and urged people to stay away from the area.

People in the northern part of Rockdale County were ordered to evacuate and others were told to shelter in place with windows and doors closed. Sheriff’s office spokesperson Christine Nesbitt did not know the number of people evacuated.

The federal Environmental Protection Agency and the Georgia Environmental Protection Division were both on site, county Emergency Management Director Sharon Webb said. The agencies are monitoring the air “to give us more of an idea of what the plume consists of.”

McDaniel said crews were working on removing the chemical from the building, away from the water source. Once the product is contained, the situation will be assessed and officials will let residents know whether it is safe to return to their homes, she said.

An evacuation center was opened at Wolverine Gym in Covington.