ATCHISON, KAS. — An inadvertent mixing of sulfuric acid and sodium hypochlorite (bleach) caused a chemical reaction at an MGP Ingredients facility on Oct. 21, which in turn led to a gaseous plume blowing over parts of Atchison, the company said Oct. 27.

MGP Ingredients said that based on the information it had, about 100 people, including three company employees, sought medical treatment related to respiratory concerns.

“We understand that all who required treatment at local hospitals have been released,” MGP Ingredients said.

The incident occurred during a routine chemical delivery by an MGP Ingredients supplier to a secured portion of the company’s property. The reaction led to emissions of chlorine gas being released into the air. Local officials reported the plume blew over an area north and west of the plant.

Once the reaction happened at about 8 a.m. on Oct. 21, employees at MGP Ingredients shut down plant operations as outlined in safety protocols and assisted first responders with evacuation procedures in the immediate vicinity of the plant. Per protocol, MGP Ingredients reported the chemical release to the Environmental Protection Agency and to Kansas and local authorities.

The E.P.A. and the Center for Toxicology and Environmental Health conducted monitoring at the plant and in the community following the incident. Local officials issued an “all clear” for community residents and local employees within three hours of the incident.

The U.S. Chemical Safety Board has begun an investigation. The Food and Drug Administration and the Occupational Safety and Health Administration also have investigated.

“At this time, we are unable to comment on investigations by various agencies, as investigations are ongoing,” MGP Ingredients said.

Plant operations are fully functional, but previously planned, regularly scheduled annual maintenance was going on the week of Oct. 23-29.