A fire this week that killed nine residents at a Fall River assisted living home has raised new questions about whether the 273 such residences in Mass. are properly staffed and equipped.

All 273 assisted living facilities in Massachusetts must send letters to all residents and families detailing fire safety protocols, evacuation procedures and key points of contact, the state announced Friday.

The fire that claimed nine lives at an assisted-living facility in Fall River, Massachusetts, "was destined to kill 50-plus people," according to the local fire chief.

Assisted living centers are rare in Mass, but many families still don’t know what they offer or how they differ from other elder care facilities.

A woman previously reported to have died after a fire at a Fall River assisted living residence remains in critical condition, the district attorney's office said.