The deadly fire at an assisted-living facility in Fall River, Massachusetts, was accidental, however, the cause is classified as undetermined because investigators found two possible origins, officials said.

The state's deadliest blaze in more than four decades has highlighted the lack of regulations governing assisted-living facilities that often care for low-income or disabled residents.

Two potential causes of the fire at the Gabriel House Assisted Living Residence in Fall River have been identified, the state fire marshal said.