By Vi Nguyen


CHICAGO (CBS)—Investigators from the National Transportation Safety Board are working with the Lake County Sheriff’s Office Friday to interview witnesses who were nearby the scene of a toxic chemical spill in suburban Beach Park on Thursday.

A firefighter who responded to the scene yesterday remains in critical condition following the massive chemical leak involving an-hydrous ammonia.

Investigators from the Environmental Protection Agency are also on the scene.

The patients include one firefighter and six others who are at Vista Medical Center in Waukegan. (Credit: CBS)

“They’ve been monitoring the ammonia level in the house as well as in the yard and other places in the area,” said Lyle Caldara, a local resident who lives on North Green Bay Road and 29th Street.

Caldara said he saw fog outside of his window Thursday as the toxic plume exploded into the sky.

“I seen the fog on the outside of the window and you could not see out the window–that was it–fog at the edge of the window.”

Residents within a one-mile radius were told to stay indoors.

School was canceled for hundreds of students as a precaution.

“I’m a former farm supplier employee and I knew all about anhydrous ammonia,” Caldara said.

It took hazmat crews hours to clean up the mess.

By the end of the day, fire officials say 40 people were taken to the hospital.

Most of them have since been treated and released, but seven people remain at Vista Hospital.

Aside from the firefighter in critical condition, six others are in serious condition.

Police say the 59-year-old driver of the tractor carrying the chemical was treated and released at the scene.

The driver was traveling from Pleasant Prairie, Wisconsin to a farm in Lake County when a leak erupted in a hose connecting two-ton containers holding the chemical.