A hot plate warmed food in the darkened kitchen in Brooklyn, allowing an Orthodox Jewish mother to feed her family while observing the Sabbath prohibition on lighting a flame. Upstairs, she and eight children slept.

That small convenience led to the city’s deadliest fire in eight years, after flames that began in the kitchen ripped through the home, trapping seven children ages 5 to 16 in their bedrooms, as their mother and a 15-year-old sister, cloaked in thick smoke, jumped out of second-floor windows. They were the only two survivors.

The authorities attributed the fire to an unknown malfunction in the electric hot plate, a device often used by observant Jewish families to keep food warm from sundown on Friday, the start of the Sabbath, until its end on Saturday night. Mayor Bill de Blasio arrived in the early afternoon on Saturday and walked inside the shell of the house with firefighters. “You can literally see what was a home for a large, strong family and now it’s wiped out, every room empty, burned and charred,” he said, adding: “This is a tragedy that has very few examples to look at, it’s so painful, it’s so difficult.”

On Saturday, investigators found a smoke detector in the basement of the home at 3371 Bedford Avenue, near Avenue L, but had not found any on the first floor, where the fire started, or the second, where the family slept. They were still searching the debris.