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 exact cause of the fire at the Gabriel House assisted living facility in Fall River may never be known, but investigators have narrowed the cause down to two possibilities, officials announced Tuesday afternoon.

Massachusetts Gov. Maura Healey is slated to meet with city officials and update the public about the response to an assisted living facility fire in Fall River that killed 10 people.

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.

River fire union has claimed more lives could have been saved if more firefighters were on scene. The mayor says the department was staffed as requested by the chief.