A massive chemical spill sent dozens of people to the hospital with respiratory problems after a toxic cloud fell over the northeastern Kansas city of Atchison Friday, Reuters reported.

The spill occurred when two substances, sodium hypochlorite and sulfuric acid, accidentally mixed at a facility belonging to MGP Ingredients Inc. The resulting concoction created a large poisonous plume, causing authorities to quickly evacuate children from local schools and urge residents to stay indoors. People were warned through radio and social media to stay away from the city of around 11,000 people located about 50 miles northwest of Kansas City until the dangerous fog dissipated.

The incident occurred around 8 a.m. local time and injured around 34 people, five being city employees from the local police, fire and public works departments. At least 52 people were hospitalized after complaining of respiratory problems and difficulty breathing.

“We could not see the trees in our yard,” resident Diann Funk told The Kansas City Star. “It was that thick. My husband could hardly breathe.”

"I honestly couldn't tell if it was fog or the chemical cloud," Megan Laflin, another local, told Reuters. "I couldn't see two feet in front of me."

2016-10-21T155043Z_1629660536_S1BEUIGTLZAB_RTRMADP_3_KANSAS-CHEMICALSPILL A fog believed by authorities to contain chemicals is seen near a police car after an incident in Atchison, Kansas, U.S. Oct. 21, 2016, in a photo provided by Debi Williams. Photo: Reuters

The effects of exposure were similar to that of mustard gas, a toxic agent of chemical warfare that produces blisters on the skin and lungs, Atchison City Manager Trey Cocking said. None of the victims treated were considered serious. However, local medical officials planned to keep them under observation for at least six hours.

The Atchison County Emergency Management updated residents in real time. Many people in public buildings such as schools, courthouses and a local airport were either evacuated or asked to seek shelter. Later in the morning, the city issued an all clear alert, maintaining that anyone showing symptoms of exposure should seek medical treatment. The Environment Protection Agency (EPA) has sent personnel to help investigate the incident.

MGP Ingredients Inc. is a supplier of distilled liquors and specialty wheat proteins and starches. The company was established in 1941 and is headquartered in Atchison. MGP employs around 200 people and was fined $6000 last March for EPA violations.