Cambria County EMA director Art Martynuska says evacuations have been ordered within a one-mile radius of the crash on Route 22 in Jackson Township.
911 dispatchers say a tractor-trailer reportedly rolled over and was believed to be hauling chlorine.
Officials say the highway will be closed for an extended period of time.
Multiple area fire departments are on scene, as well as a hazmat unit, according to dispatchers.
911 officials say no one was injured in the crash.
Martynuska adds that the crews are “working to stop the flow of the material from entering a nearby stream.”
Officials note that the Jackson Township fire department has opened its doors for anyone in need of shelter due to the evacuation notice.
Anyone seeking shelter can contact the non emergency number at 814-472-2100.