FALL RIVER, Mass. (WPRI) – Investigators have identified two potential causes of the deadly fire at an assisted living facility in Fall River, Massachusetts. But since they can’t pinpoint the exact origin, the cause of the fire has officially been ruled “undetermined.”

Bristol County District Attorney Thomas Quinn III and State Fire Marshal Jon Davine held a news conference Tuesday afternoon to release their preliminary findings.

Davine said the fire at Gabriel House began in a resident’s room on the second floor, where investigators found an oxygen concentrator and “numerous smoking materials.”

The two possible causes, according to Davine, were a malfunction of the oxygen machine or the improper use or disposal of smoking materials. Regardless of what caused it, Davine said the fire was “clearly accidental.”

“Tragically, the occupant was among those who lost their lives on July 13 and we could not speak to that resident to get an account of the fire in its earliest stages,” he added.

Davine said the presence of medical oxygen played a “significant role” in the fire.

“Oxygen is a necessary component of any fire and it was present in the area of origin and other locations at Gabriel House,” he explained. “In an oxygen-rich environment, the fire will ignite more readily and spread more rapidly and burn at higher temperatures.”

“There’s truly no safe way to smoke,” Davine added, “but smoking is especially dangerous when home oxygen is in use. No one should smoke around medical oxygen.”

The remains of a battery-powered scooter were also found in the room, but Davine said it’s believed the scooter was damaged in the fire, and was not the cause of it.

The incident remains under investigation.

The fire claimed the lives of 10 residents and sent more than 30 others to the hospital for treatment. All of the residents were also displaced, but the city helped to relocate them to other facilities, or to be with family.

When first responders arrived on scene, many residents were still trapped in the burning building due to their limited mobility. Bodycam video showed firefighters, police and EMS personnel rushing into the building and helping those people get to safety.

“There’s no doubt in my mind that that fire was destined to kill 50-plus people,” Fire Chief Jefferey Bacon said, recounting the heroic efforts of responders.

In the days that followed, the firefighters union pushed for more personnel at the fire department, saying that just two of its 10 companies were staffed to national standards. The city soon said it would increase staffing, and Gov. Maura Healey announced Tuesday that Fall River will get $1.2 million in state funding to help accomplish that. She’s also taking steps to ensure that assisted living facilities statewide have proper safety measures in place.

Mayor Paul Coogan announced Tuesday that flags at municipal buildings in Fall River will be flown at half-staff until sunset on Sunday, July 27, in honor of the victims.