Lake Township Police Chief Mark Hummer said Sunday every building in Millbury near Toledo has been searched.
Hummer says investigators are checking a nearby wooded area and a field next to the most heavily damaged part of town as a precaution.
Dozens of homes were flattened and an emergency services building was destroyed.
Lake High School, where a graduation was scheduled for today, was partially destroyed. One school bus parked near the school was thrown more than 50 yards.
A spokesperson for a local hospital says eight people were treated and released. Details were not available about the injuries. However, authorities tell the associated press that two adults and two children are in critical condition.
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WKYC-TV, The Associated Press