A chemical tank explosion in Toledo, Ohio, forced evacuations and left thousands sheltering indoors. Officials say an error caused the incident.

A chemical tank exploded in Toledo, Ohio, forcing hundreds of residents to evacuate their homes or shelter in place due to fears of a toxic release.

The site, where transport company MC Tank Transport is headquartered, identified the substance on Wednesday morning as glycidyl methacrylate, a toxic industrial chemical used in certain plastics, pain...