It happened near 190th and Halsted. Fire officials say, the U.S. Army Corps of Engineers discovered the containers while they were building an addition to an Army Reserve base.
The crews dug up containers, containing a chemical that is often used in rocket fuel. Inhaling it could cause throat and nasal irritation, or nausea and vomiting. Long term exposure could lead to liver damage.
The site was formerly used to house anti-aircraft Nike missiles for the Army.
Workers are still working to clean up the site.