NEW YORK - Seven siblings from an Orthodox Jewish family were killed early Saturday when fire tore through their Brooklyn home after they went to bed, a tragedy authorities believe was caused by a malfunctioning hot plate left on for the Sabbath.

The blaze took the lives of three girls and four boys - ages 5 to 16 - and left their mother and another child in critical condition. Officials said the flames prevented the mother, who escaped out a window, from trying to rescue her children.

"This is an unbelievable tragedy," Mayor Bill de Blasio said after touring the charred residence. "Every New Yorker is feeling this pain right now."

Investigators believe a hot plate left on a kitchen counter ignited flames that raced up the stairs, trapping the children in their second-floor back bedrooms, Fire Commissioner Daniel Nigro said.

Many religious Jews do not use electrical appliances on the Sabbath, along with refraining from work and observing other prohibitions meant to keep the day holy. Some families leave appliances on so they are usable without violating religious law.

Nigro called it the city's worst fatal fire in recent memory.

"It's a tragedy for this family, it's a tragedy for this community, it's a tragedy for the city," he said.

Police identified the victims as members of the Sassoon family: Eliane, 16; David, 12; Rivkah, 11; Yeshua, 10; Sara, 6; Moshe, 8; and Yaakob, 5.

Nigro said authorities believed their father was away at a conference at the time. Neither his name nor those of the survivors were released.

The fire broke out shortly after midnight while the children were asleep in five bedrooms in the back of the home in Midwood, a section of Brooklyn known for its low crime and close-knit Orthodox population.

Neighbor Karen Rosenblatt said she called 911 after being awakened by her husband, Andrew, when he saw flames and smoke billowing from the house. Her husband said also he heard "what seemed like a young girl scream, 'Help me! Help me!' "

Firefighters arrived less than four minutes after the 911 call to find the children's mother, badly burned and distraught, outside and pleading for help.

Investigators found a smoke detector in the basement of the house. But none were found elsewhere in the house, Nigro said, adding, "To hear a smoke detector two floors below is asking a lot."