The deadly fire at an assisted-living facility in Fall River, Massachusetts, was accidental, but the cause is classified as undetermined.

The deadly blaze that broke out at an assisted living facility in Massachusetts earlier this month was sparked accidentally by either a malfunctioning oxygen machine or, possibly, a resident smoking,

FALL RIVER, Mass. (AP) — The cause of a fire at a Massachusetts assisted-living facility that left 10 people dead remains undetermined for now as officials investigate whether smoking materials and an issue with a medical oxygen machine may have been factors, officials said Tuesday.