An apartment building fire that killed seven people was an accident caused by an electrical failure that began in a concealed space between two floors, authorities said Tuesday.
State Fire Marshal Stephen Coan said the pre-dawn fire started and burned Thursday in the void space between the second and third floors for an undetermined period, then traveled undetected along the length of the building before breaking through and getting a sudden rush of oxygen that turned it into an inferno.
"It quickly became an inferno with intense heat, and thick, black, choking smoke," he said.
The cause was announced during a news conference at a Lowell fire station 100 yards from the scene of the blaze.
Middlesex District Attorney Marian Ryan identified the victims as Torn Sak, his longtime girlfriend, Ellen Vuong, three of their five children, 38-year-old Tina Christakos and 72-year-old Robert Downs. Christakos and Downs were friends and roommates who lived in a separate apartment in the building.
Witnesses reported hearing fireworks as the blaze consumed the building. Coan said they were stored in the building and detonated at some point but didn't play a role in starting the fire. And a spokeswoman for Coan said there was no indication the fireworks caused the fire to spread more quickly.
Coan said the fire alarm system within the building was working, although the electrical failure appears to have at least partially disabled it. He said some of the 49 people who escaped the fire said they heard horn alarms in the building's hallways, but they were muffled and intermittent. Residents also had hard-wired smoke alarms with battery backups in their units. Coan said the majority of residents who were interviewed said they had heard one or both of the alarm systems.
Coan also said investigators "did not find that to be a troubled building" and had not cited the landlord for code violations.
This article was originally published on July 15, 2014.