State regulators deployed an emergency response team to the Sterigenics plant in Cobb County Tuesday to investigate a toxic gas leak that forced employees to evacuate the facility last month.

The deployment was announced hours after The Atlanta Journal-Constitution sought comment about the evacuation from officials with the Georgia Environmental Protection Division.

The AJC obtained a company email to employees indicating the leak occurred in the early morning of July 31. The night before, hundreds of residents attended a community meeting at a Smyrna middle school to discuss toxic ethylene oxide emissions from the plant. The facility uses the carcinogenic gas to sterilize medical equipment.

“I wanted to inform each of you that we experienced an area evacuation at approximately 3:14 a.m. this morning,” the email reads. “An investigation took place at this time and it was found that a drum that was recently removed … was leaking from the gas valve.”

The email goes on to say that the valve was closed, but does not say how much ethylene oxide might have escaped. The company is required to report a leak immediately if the size of the release cannot be determined, or if it’s greater than 10 pounds.

After the leak was sealed, “The levels that were seen in the facility at the time dissipated as well,” the email reads.

Sterigenics issued a statement to the AJC following the emergency response team deployment, saying the release was detected by sensors in the plant and was determined to be less than six pounds — below the reporting threshold.

“The detection sensors are designed for the protection of the employees in the facility as well as the broader community and are calibrated to provide release alerts even at levels well below the EPD’s requirements for reporting,” the statement said. “Although this release was below the level required to be reported to the EPD, Sterigenics took immediate corrective actions to ensure similar incidents do not occur in the future.”

The EPD said it could not conclude, based on the email, whether a reportable release occurred. All emissions, both permitted and accidental, are self-reported to the state by the company.

Gov. Brian Kemp’s spokeswoman, Candice Broce, said the EPD visited the plant in response to “new information.”

Sterigenics officials, along with executives from a Covington sterilization company, met with Kemp last week after sustained community protests by residents concerned about the levels of ethylene oxide emissions from the plants. Community organizations and Democratic lawmakers have called for Kemp to shut down both facilities at a series of town hall meetings.

Kemp urged the executives to take new measures that would “build trust” with outraged residents.

State officials said Sterigenics did not notify them of the evacuation, despite assurances of transparency, including during the meeting with the governor. The government officials asked to remain anonymous because they were not authorized to speak about the private discussions.

Sterigenics has already been reprimanded by state regulators for failing to report an ethylene oxide leak in April of 2018. In July of that year, an explosion seriously injured a worker. The EPD concluded that no hazardous material had been released during the explosion, based on the company's report.

“Now that EPD has been made aware of the potential release on July 31st [of 2019], EPD is conducting an investigation of this incident,” the agency said in a statement. “Following that investigation, EPD will determine the appropriate next steps.”

Reporter Greg Bluestein contributed to this story.

Sterigenics statement in full:

“On July 31, 2019, the ethylene oxide (EO) detection sensors at the Sterigenics Atlanta identified a potential release of EO at a localized area within the facility. The detection sensors are designed for the protection of the employees in the facility as well as the broader community and are calibrated to provide release alerts even at levels well below the EPD’s requirements for reporting. 

“On July 31, the sensors appropriately alerted employees in the vicinity of a potential EO release. Consistent with company procedures, employees properly vacated the area and the incident was immediately investigated. The source of the release was immediately identified and stopped. It was determined that less than six pounds of EO was released from a used EO drum on which the valve was not completely closed after use. Although this release was below the level required to be reported to the EPD, Sterigenics took immediate corrective actions to ensure similar incidents do not occur in the future.”