"My girls are in my heart," Madonna Badger told more than 500 mourners at St. Thomas Church in Manhattan. "They're right here. And that's where they live now."
Badger broke down several times as she described each girl in turn - Lily, 9, and 7-year-old twins Sarah and Grace - then wailed as she followed their coffins out of the cavernous Gothic church. She was accompanied by her estranged husband, Matthew Badger.
Badger's parents, Lomer and Pauline Johnson, also died in the fire.
Badger told mourners, "In all the incomprehensible loss and chaos, all I can hang onto is that love is everything."
The pallbearers were 18 firefighters from Stamford, Conn., who responded to the fire. Among the more than 500 people attending the service in New York City were fashion designers Calvin Klein and Vera Wang, rocker Lou Reed and actor Philip Seymour Hoffman.
Madonna Badger is a fashion advertising executive who worked on Calvin Klein campaigns.
Stamford Mayor Michael Pavia also attended the service at a century-old Episcopal church.
Three blonde girls wearing pretty dresses laughed delightedly in a photo that adorned the program for the service.
Badger said Lily was "my angel and my life and she was my firstborn." Sarah was "my little whippersnapper, loved and lovable and full of love." Grace was "fearless" but often asked her mother "if she was going to die before me."
"I said no, that's never going to happen," she said. "But it did, and I wonder why. Why my children? Why my parents?"
Singer-songwriter Rufus Wainwright performed a haunting a cappella version of "Over the Rainbow" during the service, which also featured hymns sung by St. Thomas' all-male choir.
A private service was held later at Woodlawn Cemetery for the girls and their grandparents.
Authorities have told The Associated Press that embers in a bag of discarded ashes started the blaze. They had been taken out of a fireplace so the children wouldn't worry about Santa coming down the chimney.
Madonna Badger and a friend, Michael Borcina, were treated at a hospital.
Fire officials have said Borcina is believed to have placed the ashes in or outside an entryway, near the trash.
The victims died of smoke inhalation. Grandfather Lomer Johnson also suffered a blunt head and neck trauma, which resulted from a fall or being hit by an object.
One of the girls, found dead just inside a window, had been placed on a pile of books, apparently so Johnson could reach in and grab her after he jumped out. Instead, authorities say, he fell through the roof.
Stamford police are helping fire officials investigate the blaze. Police said Monday officials want to know whether there were smoke alarms, the status of renovation work on the house and whether the contractor had permits.
The issue of permits could figure in the investigation because the Connecticut Department of Consumer Protection has said that neither Borcina nor his company, Tiberias Construction Inc., was registered to perform home improvement work in Connecticut.
Contractors are required to register with the state, though numerous building and other permits are issued by local officials.
The agency said it did not yet have enough information about what work may have been done or completed and would not comment on whether it will investigate.
Facebook messages have been left for Borcina. Repeated attempts to contact him since the fire have been unsuccessful. He attended the service but did not speak to reporters.
Stamford authorities deemed the house unsafe following the fire and ordered it torn down the day after.
Fire Chief Antonio Conte said the fire was Stamford's deadliest since a 1987 blaze that also killed five people.
Associated Press writer John Christoffersen in Connecticut contributed to this report.
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