The investigation is complete into an fire that destroyed a senior assisted-living complex that was just about to open in Waterloo. Officials looking into the cause have concluded the blaze was set, but not necessarily on purpose. Last Wednesday, fire leveled the "Rose of Waterloo," a 64-unit, three-story building that was scheduled to open later this year.

Local officials asked federal authorities for help in finding the cause, because of the large amount of damage done. A national response team from the U.S. Bureau of Alcohol, Tobacco, Firearms, and Explosives was called to the scene, and the federal investigators finished their search of the site over the weekend. They determined that a person or people started the fire, but the intent isn’t known.

They stopped short of labeling the cause arson, because the fire may have been an accident — possibly started by a homeless person to keep warm. The fire caused more than eight million dollars in damage. A $15,000 reward is being offered for information that leads to an arrest and conviction in the case.

Audio: Elwin Huffman report. :48 MP3

Radio Iowa