The Nebraska State Fire Marshal’s Office has determined that Sunday night’s explosion and fire at Winfrey Plumbing and Heating here resulted from the manufacturing of homemade explosives by the man who died in the fire.

A severe weather outbreak gearing up to hammer the country’s midsection on Tuesday could spawn sustained, muscular tornadoes as well as softball-size hail showers, say forecasters, who also warned of additional rounds of storms to follow.