BEACH PARK, Ill. (AP) — The Latest on a chemical leak in a northern Chicago suburb (all times local):

5:20 p.m.

The National Transportation Safety Board is sending a team to Illinois to investigate a chemical release from two containers that caused a toxic plume that sickened dozens of people.

The NTSB announced the team of four will be on the scene in Beach Park on Friday, when it will begin work.

Authorities say a tractor was towing two separate two-ton containers of anhydrous ammonia when the leak occurred around 4:30 a.m. Thursday. Initial reports suggested the vehicle was involved in a crash, but the sheriff's office later said that was not the case.

The leak created a toxic cloud that lingered for several hours over Beach Park, about 40 miles (65 kilometers) north of downtown Chicago. Authorities ordered residents within a 1-miles radius to stay inside and close their windows. Area schools were closed for the day.

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12:40 p.m.

Authorities say 11 firefighters and three police officers are among 37 people hospitalized due to an ammonia leak in a northern Chicago suburb.

Officials say the chemical leaked from a container being hauled behind a tractor in Beach Park about 4:30 a.m. Thursday, releasing toxic plumes into the air.

The Lake County Sheriff's Office says seven of those hospitalized are in critical but stable condition, including one firefighter. Sheriff's spokesman Christopher Covelli says the three officers are in good condition.

Covelli says the first two officers who responded to the leak had to retreat because they were overcome by fumes.

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11:15 a.m.

Authorities say 37 people have been hospitalized due to an ammonia leak in a Chicago suburb.

Lake County Sheriff's spokesman Christopher Covelli says three law enforcement officers are among those taken to hospitals after the leak in Beach Park early Thursday, and that they are in good condition.

Covelli says several other people are in serious but stable condition. Authorities say most of those injured suffered breathing problems.

The Centers for Disease Control and Prevention says anhydrous ammonia is a colorless gas that can cause breathing difficulties, burns, blisters and is fatal if inhaled in high concentrations.

Residents within a 1-mile radius of the leak were initially told to close their windows and remain indoors, but that order was lifted a few hours later. Schools in the area are closed.

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9:35 a.m.

Authorities say 31 people have been taken to hospitals after anhydrous ammonia leaked from containers that a tractor was pulling in a Chicago suburb.

Lake County Sheriff's spokesman Christopher Covelli said Thursday that the number of hospitalized includes three law enforcement officers who are in good condition. Covelli says several others are in serious but stable condition.

Authorities say the leak happened at about 4:30 a.m. Thursday and causing toxic plumes of the chemical to be released in the air over Beach Park, about 40 miles (65 kilometers) north of downtown Chicago.

Authorities initially asked any residents within a 1-mile radius of the leak to close their windows and remain indoors. Covelli says that shelter-in-place order is being lifted at 10 a.m.

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9:20 a.m.

Authorities say an anhydrous ammonia leak in north suburban Chicago has been contained.

Lake Forest Fire Chief Mike Gallo says a tractor was towing two separate 2-ton containers of the chemical that farmers use for soil early Thursday. Gallo says the leaking tank is now empty.

No information has been provided about how the leak occurred. Initial reports said the tractor was involved in a crash but authorities now say it doesn't appear there was a collision.

Authorities are waiting for the chemical plume to dissipate. Gallo says the weather is good in the area and that's helping.

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8:40 a.m.

Authorities say hospitals are treating between 12 and 15 people who are in serious but stable condition after anhydrous ammonia leaked from containers that a tractor was pulling in a Chicago suburb.

Lake County Sheriff's spokesman Sgt. Christopher Covelli says those injured Thursday morning include two deputies who first responded to the chemical spill. He says the deputies had to retreat when they were overcome by the chemical fumes.

Covelli says the tractor driver also was taken to a hospital. The spill happened in Beach Park, about 40 miles (65 kilometers) north of downtown Chicago.

Covelli says officers are going door-to-door near the spill to check on residents. Residents within a 1-mile radius have been asked to close windows, turn off ventilation and stay indoors. Covelli says it could be hours before that order is lifted.

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7:25 a.m.

A police spokesman says a toxic gas cloud that's forced residents in a suburban Chicago community to stay indoors with their windows closed is coming from a leaking tanker that was involved in a crash.

Lake County Sheriff's Office spokesman Sgt. Christopher Covelli says the first deputies on the scene had to retreat because they were immediately overcome by the strong fumes. The department believes the spilled substance is anhydrous ammonia.

Covelli says a tractor was pulling the tanker when it crashed about 4:30 a.m. Thursday and the toxic fumes began leaking, creating "a cloud of this toxic chemical."

Covelli says there are reports of injuries but he doesn't have details.

He says people within a 1-mile radius of the crash scene at Green Bay Road and 29th Street in the north suburban community should stay indoors with their windows closed while hazardous materials crews try to stop the leak.

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6:27 a.m.

Authorities are urging residents in a suburban Chicago community to stay indoors with their windows closed following a chemical spill that resulted in a toxic gas cloud.

The Lake County Sheriff's Office reported the hazardous material spill just before 5 a.m. Thursday in Beach Park, saying the spill has created "a dangerous chemical cloud" in a 1-mile radius of Green Bay Road and 29th Street in the north suburban community.

The sheriff's department says the spill appears to be anhydrous ammonia.

Residents are being urged to stay inside with their windows closed while hazardous materials crews respond to the spill.

The Centers for Disease Control and Prevention says anhydrous ammonia is a colorless gas that can cause breathing difficulties, burns, blisters and can be fatal in high concentrations.