A fire that killed 10 people at a Massachusetts assisted-living facility was unintentionally caused by either someone smoking or an electrical issue with an oxygen machine, investigators said Tuesday.

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,

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

An investigation into the source of the fatal fire at a Massachusetts assisted living facility last week classified the cause as "undetermined," though officials believe it was an accidental ignition

State Sen. Mark Montigny to ask Assisted Living Commission to extend its reporting deadline in wake of tragic fire at the Fall River Gabriel House.

All 273 assisted living facilities in Massachusetts will be required to send a letter to all residents and families detailing fire safety protocols.

More than 75 percent of Gabriel House residents are enrolled in Medicaid, state officials have said, and it charges significantly less than a typical assisted living facility does for private-paying patients.