A Passover observance turned deadly yesterday morning when a stove left on, in keeping with chasidic practice, caused a fire at a Williamsburg apartment that killed two teenage brothers and their 7-year-old nephew.

Four other family members, three neighbors, and three firefighters were injured.

Shortly before 6 a.m., neighbors were awakened by screams coming from a second-floor apartment. Many watched as members of the Matyash family pounded on the windows, shrieking for help. Symah Matyash; his wife, Rachel; four of their children, and one of their grandchildren were trapped in their apartment at 104 Ross St. Officials said the fire originated from an open flame on a stovetop and blocked the family’s path to the front door.

The panicky pleas prompted a neighbor to throw stones at one of the second-story windows, shattering it in time for the two sisters of the family, Sara, 21, and Gitty, 18, to leap out.

Sara Matyash sustained injuries, including a broken leg, and was taken to New York Hospital-Cornell Medical Center yesterday afternoon for surgery, according to Anna Matyash’s brother-in-law, Moshe Weiss.

When firefighters reached the apartment, the three boys were all found unconscious, one lying in the bedroom, the other two in the living room and adjacent hallway, a spokesman for the Fire Department, Paul Iannizzotto, said. They were pronounced dead at area hospitals.

Mr. Weiss said the brothers who perished were Shia, 15, and Yidel, 13. The 7-year-old’s boy’s name was Israel Falcowitz. His nickname was Shlomie, Mr. Weiss said.

A sixth-floor resident of the apartment complex, Mimi Perez, said she witnessed the youngest boy’s removal from the building.

“Every time I close my eyes I can see the image of that little boy in the fireman’s arms,” Ms. Perez said after encountering the firefighter and the boy in the stairwell. “It reminded me so much of that photograph from the Oklahoma City bombing.”

The teenage boys’ father is a locally known chef. He and his wife were rushed to Long Island College Hospital and treated for smoke inhalation. Anna Matyash was released from the hospital shortly before her grandson’s funeral at 2 p.m. Her husband’s condition could not be ascertained.

The youngest boy who died was staying with his grandparents because his mother, a sister of Sara and Gitty, had just given birth to another son and was staying with her husband in another part of Brooklyn.

More than 100 community residents attended the 6-year-old’s funeral, held at a synagogue on Keap Street only hours after his death.

Fire officials believe the Matyash family had ignited the stove Friday before sundown and left it burning through the weekend, in accordance with Judaic law, which forbids starting or extinguishing fire during the Sabbath or the first two days of the Passover holiday.

According to the Fire Department’s Mr. Iannizzotto, three fire trucks responded to the fire within three minutes and 50 seconds, nearly half a minute faster than the city’s average response time. The fire was first reported at 5:52 a.m. and was reported under control at 6:26 a.m.

Fire officials said approximately 75 firefighters responded to the call. Three firefighters were slightly injured during the search-and-rescue operation and taken to Wyckoff Hospital, where they were treated and released.

Any concerns residents might have expressed about tardy response times, and about delays caused by the Bloomberg administration’s closing in 2003 of the Williamsburg firehouse housing Engine Company 212, were ill-founded, Mr. Iannizzotto said. He said the first fire truck to arrive at the apartment had to travel only two blocks.

Other onlookers voiced concerns about the top-to-bottom “childproof” security bars in the apartment windows and the possibility of being entrapped with no means of escape.

According to Ms. Perez, the bars had been reinforced several years ago after a child fell from the window. She worries now that the bars, which city law requires in residences with young children and without fire escapes, may be seen as a hazard more than a precaution.

“The bars are screwed in,” Ms. Perez said. “They can only be opened with a screwdriver, and in that situation there is not time to get a screwdriver.”

The security bars on the Matyash household, however, were not viewed as a threat by the Fire Department, nor were they deemed responsible for the deaths of the three boys, Mr. Iannizzotto said.

“The two parents were removed with no problem from the window guards,” he said, later adding that if the gates had posed a problem, the firefighters would have radioed for special equipment.

“The two girls probably were panicked and couldn’t figure out how to open the window,” he said.

The deaths came shortly after the Fire Department and members of the New York Board of Rabbis went to Williamsburg and Greenpoint to educate worshippers and distribute information about fire precautions and safety tips for the Passover holiday.

Mr. Weiss echoed the Fire Department’s concern for Passover precautions yesterday.

“This tragedy could happen to anyone,” he said. “This just suggests that we, in this community, should be more careful with candles and cooking on this holiday.”

The deaths of the three boys shocked the tight-knit chasidic community, which gathered outdoors near the apartment, amid the shards of glass and charred windows.

“When a tragedy like this happens to one of us, it happens to all of us,” Mr. Weiss said.

Preparations for the two teenage boys’ funerals will take place when Mr. Matyash is released from the hospital, Mr. Weiss said yesterday afternoon, after attending the younger boy’s funeral.