MAEBASHI, Gunma Pref. (Kyodo) Police plan to pursue a charge of professional negligence resulting in death and injury against the operator of a nursing home in Gunma Prefecture where 10 elderly residents were killed in a fire last week, investigators said Monday.

The Gunma Prefectural Police found what appears to be a piece of a lighter, which could support an allegation that nonprofit nursing home operator Saikeikai failed to properly manage smoking by the home's residents.

Police are investigating whether insufficient safety steps by the Tamayura nursing home in Shibukawa, coupled with the buildings' complicated layout resulting from repeated extensions and renovations, may have exacerbated the damage caused by the fire.