South Plainfield mayor Matthew Anesh says smoke alarms were not working in a portion of a home when a fire killed five members of a family -- four of them children.

Anesh says authorities are still investigating the cause of the fast-moving blaze.

However, home-owner Gerado Avalos tells The Star-Ledger that smoke detectors were installed and he checked them in October. Thursday's early morning fire was the deadliest on record for the borough, which is about 30 miles southwest of New York City.

Relatives have identified the fifth victim as the children's grandmother, although authorities say they are still working to identify the dead and haven't released their names.

Authorities say four other members of the family were injured in the blaze. One remained hospitalized Thursday.

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