Authorities have determined that a fire that killed four people in Lynn a month ago started in the front stairwell, but the cause of the fire remains undetermined.
"An electrical fire is a possible cause, and while there are no obvious signs of foul play, an arson fire cannot be ruled out, nor can smoking be totally eliminated as a possible cause," investigators said in a joint statement, which added that standards require a blaze be left undetermined "if investigators cannot eliminate all but one most probable cause."
The Monday statement concludes the investigation into the Dec. 4, 2015, fire that swept through a three-unit apartment building at 24 Bruce Place.
In addition to killing four people, the blaze injured two others and displaced 22 residents of the building.
The four people who died lived on the second floor, investigators said, and were trapped by the fire. The investigation determined the fire started in the building's front stairwell, which the statement said was "normally used by the second floor tenants to access their units."
The four who died were previously identified by medical examiners as 42-year-old Maritza Cruz Vizcaino, 36-year-old Sonia Cruz, 20-year-old Yasmin Cruz and 28-year-old Rodolfo Cruz. The victims were all related.
The statement also addressed an apparent lack of enough smoke alarms:
Witnesses heard no smoke alarms from the hallways, only from inside the apartments themselves. This leads investigators to believe there were no working smoke alarms in the front hallway either. This allowed the fire to get a huge head start before anyone was alerted to the early morning fire. The smoke had to enter the individual apartments where those smoke alarms gave people the first warning signs of danger, leaving them little or no time to escape.
The state Department of Fire Services will issue a non-criminal notice of violation to the landlord for "failure to maintain fire protection systems."
With reporting by WBUR's Newscast Unit and Benjamin Swasey