Beach Park, Illinois — Plumes of a toxic gas that leaked in a northern Chicago suburb Thursday morning sent at least 37 people to hospitals and prompted an order for residents to stay locked inside their homes with windows shut tight, officials said.
A tweet sent Thursday afternoon by the Lake County Sheriff said seven people are in critical but stable condition.
Three law enforcement officers who responded to the leak in Beach Park were among those injured and they were in good condition, Lake County Sheriff's spokesman Christopher Covelli has said.
Lake Forest Fire Chief Mike Gallo said a tractor was towing two separate two-ton containers of anhydrous ammonia when the leak occurred around 4:30 a.m. Initial reports suggested the vehicle was involved in a crash, but Covelli later said that was not the case. The cause of the leak has not been released.
The leak created a toxic cloud that lingered over Beach Park, about 40 miles north of downtown Chicago.
"This is a very dangerous chemical that can cause unconscious and worst-case scenario death," Covelli said.
According to the Centers for Disease Control and Prevention, anhydrous ammonia is a colorless gas that can cause breathing difficulties, burns, blisters and is fatal if breathed in high concentrations. Farmers use it to add nitrogen to soil.
The first two officers who responded to the leak had to retreat because they were overcome by the ammonia, Covelli said.
"It was difficult to get to that scene initially with those chemicals in the air without proper protection and gear to wear over the face," he said.
Authorities said about two dozen law enforcement agencies responded to the leak, including a hazardous materials team. The leak was contained within a few hours and the leaking tank was empty, authorities said, adding that they were waiting for the chemical plume to dissipate.
Residents within a one-mile radius of the leak were initially told to close their windows and remain indoors, but that order was lifted at 10 a.m., Covelli said. Later Thursday morning, officers went door-to-door in the area to check if anyone was in medical distress, Covelli said.
Schools in the area were closed Thursday including all schools in Beach Park School District 3.