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 Massachusetts assisted-living facility where a fatal fire killed nine people was caring for dozens of aging residents reliant on wheelchairs and oxygen tanks, but it lacked the safety measures and most of the staffing requirements that are commonplace in nursing homes.

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.