A Sunday night fire at an assisted living facility in Fall River that took the lives of nine residents has left the dozens of the home’s surviving residents in need of basic essentials.

River firefighters union says low staffing levels prevented them from rescuing more people in Massachusetts deadliest fire in 40 years.

Local and state fire investigators are working to identify the origin and cause of the 5-alarm at Gabriel House on Oliver Street, officials said.

As flames tore through a Fall River assisted living residence Sunday night, nearly 50 firefighters rushed to rescue the vulnerable population calling for help from their windows. The fire killed nine residents and injured 30 at the Gabriel House Assisted Living Residence.