Just weeks after a family celebrated the holidays at their $6 million Annapolis mansion, a towering Christmas tree fueled a fire that took the lives of four children and their grandparents, fire officials said Wednesday.

A faulty electrical outlet powering tree lights in the home’s Great Room — which had 19-foot-high ceilings and was connected to the sleeping and living areas — likely ignited the Jan. 19 blaze by setting the tree skirt on fire, officials said. It killed homeowners Don and Sandra Pyle, along with two sets of Boone siblings: Lexi, 8, and Katie, 7; and Charlotte, 8, and Wes, 6.

“While the explanation that has been shared with us today does not bring solace,” the family said in a statement Wednesday night, “it does start us down the long road to acceptance.”

The 15-foot-high Fraser fir, cut 65 days earlier and purchased in early December, provided a concentrated source of tinder that propelled the fire’s ferocious spread through the 16,000-square-foot house, fire officials said. The tree was lit 24 hours a day.

All six died of smoke inhalation and burns, said those familiar with the case. Anne Arundel County Fire Chief Allan Graves wouldn’t confirm that, saying investigators had yet to receive the final report from the medical examiner.

Out of respect for the family, fire officials also declined to say where the bodies were found or whether it appeared that anyone had tried to flee.

“This fire was the result of a tragic accident that occurred at the absolutely worst possible time: while the Pyles and their grandchildren were sleeping,” said Bill McMullan, who heads the Bureau of Alcohol, Tobacco, Firearms and Explosives office in Baltimore.

The size of the tree combined with the oxygen available in the house’s cavernous rooms created an inferno, fire officials said. It became so large and fast-moving that it may explain why no one was able to escape.

They may have been trapped even if alarms alerted the family, said Jim Milke, chairman of the University of Maryland’s fire protection engineering department. A large, dry tree would have produced “a tremendous amount of heat in a very short order,” he said.

Residential blazes that begin with Christmas trees are three times as deadly as home fires in general, a study by the National Fire Protection Association found.

Between 2007 and 2011, the association said, U.S. fire departments responded to an average of 230 home fires a year that started with Christmas trees. Electrical problems were a factor in a third of those cases.

In controlled burns, fresh, six-foot trees went up in 90 seconds, while trees that had been dried for two weeks were consumed in half that time, said Isaac Leventon, a doctoral student in fire protection engineering at Maryland.

“The longer you keep it, the drier it is going to get,” Leventon said. “It’s going to take off, and it’s going to grow quickly and catch anything nearby on fire.”

In Annapolis, investigators have ordered three trees of similar size that they plan to dry out and use to replicate the blaze.

The fire — one of Maryland’s deadliest in years — began during a sleepover Jan. 18 at the Pyles’ waterfront home, which was built to resemble a castle, with statues of winged lions, a suit of armor, antler chandeliers and spiral stairways inside turrets. Don, a 56-year-old tech executive, and Sandra, 63, had taken their grandchildren to Medieval Times at the Arundel Mills mall, where they watched knights jousting and ate banquet food before returning home that night.

An alarm system alerted 911 at 3:30 the following morning that smoke had been detected on the mansion’s first and second floors. Fire officials confirmed Wednesday that the smoke alarms had functioned properly, but the four-alarm fire still quickly ravaged the house, which did not have a sprinkler system.

The blaze raged for three hours before more than 80 firefighters could contain it.

Left behind are brothers Clint and Randy Boone, who each lost two children as well as their mother and stepfather in a single night.

Clint, 37, and his ex-wife, Eve Morrison, 39, are parents to Charlotte and Wes.

Randy, 38, and Stacey, 34 — parents to Lexi and Katie — also have a newborn son, who was at home with them the night of the fire.

All four children were students at the private Severn School, where the family was such a fixture that a parking space was marked, “Reserved for Pyle Family.”

Learning the fire’s cause on Wednesday only added to the family members’ anguish. “Our hope,” they said in their statement, “is that our loss will raise awareness that this tragic event could happen to any family.”

For six days, crews sifted through concrete, charred wood and ash as they painstakingly searched for the six bodies. Investigators found the remains of five within the first 72 hours of the search and worked through the weekend — in rain and snow — before recovering the final body Monday.

Anne Arundel received help with the massive investigation from the ATF, the state Fire Marshal’s Office and several neighboring fire departments.

Fire officials said that if the home had been equipped with sprinklers, it might have prevented — or at least lessened — the disaster. The Pyle mansion was built in 2005, four years before Anne Arundel required sprinklers in new residential homes.

Starting in June, Maryland will become the second state in the country, after California, to require sprinklers in all new residential buildings.

The Boones have repeatedly thanked the firefighters who searched for their loved ones and the community for its support.

“As we work through our pain and loss,” they said Wednesday, “the memories we made with our family will sustain us.”