The Williamsburg fire that killed a grandmother Monday night was likely the result of an electrical problem, the FDNY says.

Officials say Patricia Serrano was trapped in the Metropolitan Avenue building as it burned around 10:45 p.m. Rescuers brought her to Woodhull Hospital in critical condition, but she later died from her injuries. They say four other people sustained minor injuries. The fire also killed a dog.

The building had no working smoke detectors, according to officials. They say the blaze began in a first-floor apartment and spread upward in the six-story building. Serrano lived on the third floor.

According to officials, the building was inspected within the last 24 hours for faulty wiring. 

Serrano was a retired medical assistant and an active member of the Williamsburg community, neighbors say. She attended the nearby senior center and volunteered at a food pantry on Tuesdays.