The Latest: Wisconsin tractor leaked ammonia in Illinois

BEACH PARK, Ill. (AP) - The Latest on an ammonia leak in a Chicago suburb that injured dozens (all times local):

1:35 p.m.

Authorities say a tractor driver was towing tanks of ammonia from a farm in Wisconsin to a farm in Illinois when the chemical leaked, creating a toxic gas cloud that injured dozens of people in a Chicago suburb.

Lake County Sheriff's spokesman Christopher Covelli said Friday that the 59-year-old man was traveling from a farm in Pleasant Prairie early Thursday when the leak happened in Beach Park. No explanation has been provided on the cause of the leak.

Authorities have said 37 people ended up in hospitals, mainly with breathing problems, and seven of those remain in intensive care Friday.

Covelli says the man driving the tractor and its owner are cooperating with authorities.

He says the John Deere tractor was towing two 1,000-gallon side-by-side tanks when the leak occurred in Beach Park, about 40 miles (65 kilometers) north of downtown Chicago.

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9:35 a.m.

Seven people, including a firefighter, remain in intensive care after they were injured in an ammonia leak in Illinois.

Lake County Sheriff's spokesman Christopher Covelli said Friday that the majority of the 37 people injured Thursday have been treated and released from hospitals. Toxic gas plumes formed and lingered for several hours when anhydrous ammonia leaked from containers being pulled by a tractor in Beach Park, about 40 miles (65 kilometers) north of downtown Chicago.

The injured included 11 firefighters and three police officers.

Sheriff's detectives and a team from the National Transportation Safety Board are jointly investigating the leak Friday.

Covelli told the Daily Herald it could be more than a week before a cause is determined.