The cause of deadly fire at the Gabriel House assisted living home in Fall River, Massachusetts last week is still officially undetermined, but investigators have narrowed it down to two possibilities: smoking or the failure of a resident's oxygen device.

The state’s fire marshal said the fire was either caused by an electrical or “mechanical failure” involving the oxygen device, or by improper use of smoking materials.

Smoking or an oxygen machine issue may have sparked the deadly fire at Gabriel House Assisted Living Facility in Fall River, Massachusetts, a state fire marshal said.