A fast-moving house fire in southern New Jersey that killed four family members, including a four-month-old baby, has been ruled an accident, authorities said Wednesday.

Two women, an infant and a teenage girl died in Tuesday's fire in Lacey Township, Ocean County Prosecutor Bradley Billhimer said. Another woman who also lived there was able to escape the residence before the roof collapsed, which forced firefighters to evacuate.

The fire in the two-story home was reported around 12:30 p.m. The home was engulfed in flames when firefighters arrived, and black smoke spewed throughout the neighborhood. No other homes were damaged.

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Investigators have determined that the fire started on the porch on the west side of the home, Billhimer said, adding that "improperly discarded smoking material cannot be eliminated" as the cause of the blaze.

The victims were identified as Jennifer Wright, 39; Alaina Wright, 34; a 14-year-old girl and a four-month-old baby, Billhimer said.

Brenda Wright, 67, was able to escape the flames but suffered undisclosed injuries. She remained hospitalized Wednesday in stable condition.