Five dead in Illinois crash involving semi-truck carrying ammonia, residents cannot return home yet

At least five people were killed and parts of an Illinois neighborhood were evacuated due to a Friday crash involving a semi-truck carrying thousands of gallons of anhydrous ammonia.

The truck was carrying about 7,500 gallons of the toxic substance at the time of the wreck in Effingham County, according to the Illinois Environmental Protection Agency. The agency said early estimates say more than half of that - about 4,000 gallons - were released.

The leak has been "partially patched" and approximately 500 people have been evacuated from the area, according to the state EPA. In addition to the deaths, there have also been multiple injuries.

Parts of Teutopolis, a village in south-central Illinois, were evacuated "due to the plume from the ammonia leak" after the crash Friday night on US Highway 40, about a half mile east of Teutopolis, Illinois State Police said.

Emergency crews were still on scene and working to contain the leak Saturday afternoon, according to the state's EPA.

Just before 5 p.m. a separate crash had taken place on Interstate 70 just east of Effingham, which caused traffic to be rerouted to US Highway 40.

At about 9:25 p.m. local time, authorities were notified about a crash on the highway "involving multiple vehicles, including a semi-truck that is leaking anhydrous ammonia," police said.

Effingham County Sheriff Paul Kuhns described the scene as large and complicated.

At least five people were airlifted to local hospitals, Teutopolis Fire Chief Tim McMahon said.

Crews worked overnight to get part of the rupture on the semi-truck patched up - which slowed down the leak but did not stop it completely, according to McMahon.

Those within an estimated 1-mile radius of the crash, including northeastern parts of Teutopolis, were then evacuated, police said.

The evacuation orders continued early Saturday, and a shelter was set up for those affected.

There is no time period for when residents will be able to return home, Kuhns told reporters Saturday morning.

Anhydrous ammonia "is essentially pure (over 99 percent) ammonia," according to the Occupational Safety and Health Administration. "'Anhydrous' is a Greek word meaning 'without water;' therefore, anhydrous ammonia in ammonia without water."

Ammonia used in households is a diluted water solution that contains 5 to 10 percent ammonia, according to OSHA.

Ammonia in high levels can irritate and burn the skin, mouth, throat, lungs and eyes, according to the Centers for Disease Control and Prevention. Very high levels can also damage the lungs or cause death.

Symptoms of anhydrous ammonia exposure include breathing difficulty; irritation of the eyes, nose or throat; and burns or blisters.

Anhydrous ammonia can get into airways and attach itself to mucus and moist surfaces, Kuhns said. "It caused terribly dangerous air conditions," he said of the leak.

Effingham County has an estimated population of about 34,000 according to the US Census Bureau, and is located about two hours south of Illinois' capital, Springfield.

CNN's Zoe Sottile and Raja Razek contributed to this report.