BOISE — Boise firefighters believe working smoke detectors could have helped save the lives of a woman and her two children who died in a house fire early Monday morning.

The Boise Fire Department responded at about 5 a.m. to a house fire in the 1500 block of South Leadville Avenue. When they searched the home, they found a woman, Jana Cullen, 43; a boy, Ryker Sanchez, 12; and a 9-year-old girl later identified as Rilee Sanchez. Char Jackson, spokeswoman for the Boise Fire Department, confirmed Cullen was the mother of the Sanchez children.

Although first responders performed CPR on them and rushed the two children to Saint Alphonsus Regional Medical Center, all three died.

Fire investigators determined the fire to be an accident, according to a news release from the Boise Fire Department. A heating element had failed inside a burner used to burn fragrant wax and ignited shelving inside the home.

The fire itself was small, Boise Deputy Fire Chief Romeo Gervais said at a press conference Monday. That’s typical of fires in small, tight homes — the fire suffocates because there is little oxygen. Boise firefighters knocked down the flames without much difficulty, Gervais said. The problem was the smoke.

Gervais said there were no working smoke detectors in the home. Some had been removed and others didn’t have batteries.

That’s not uncommon in the case of fatal fires, Gervais said. Smoke detectors are designed to alert the residents of a home to the presence of a fire. It gives them a few extra minutes to escape a burning building.

“It’s a fair statement that over the course of my career, a working smoke detector has made the difference between a fatal structure fire and just a structure fire,” Gervais said.

Monday’s fire is the deadliest in recent memory, Gervais said. The department has checked data back to 2011, and no fire has claimed more lives than Monday’s. Even the Oregon Trail Fire of August 2008, which burned 60 homes in Boise, took less of a toll in human life.

Gervais implored residents on Monday to make sure they have working smoke detectors. He said if residents are having problems with them, they should call the Boise Fire Department. He also said there are programs available for those who cannot afford smoke detectors.

He said it was “very emotional” to have to address the public in such a way.

“I don’t want to have to be up here again, saying this,” he said.

The fire was also emotional for Gracie Tostenson, who lives in an apartment across the street from the house where Cullen and her children died. She awoke early Monday morning and could see the fire department vehicles lining her street, but it took some time until she saw flames in the house’s living room. She watched as firefighters pulled people from within the burning building, she said.

“It was really hard to watch,” she said.

Across the street from her, Julianna Nemeth also stepped out of her apartment. She, herself, didn’t see flames.

“I was smelling a little smoke, but nothing too strong,” Nemeth remembered.

Tostenson said she remained outside her apartment for most of the day, watching as first responders cleared the scene. She kept watching as her usually quiet, shaded side street, just off Broadway Avenue, filled with cars as people slowed by the house to look at it. She didn’t understand what they were looking for, or the appeal.

Neither did Kevin Hennessey, another resident of the neighborhood who had watched as firefighters tried to save the lives of the house’s residents.

“What do you think you’re going to see?” he asked.

Tostenson, Hennessey and Nemeth could not remember a time the street had been so busy.

Tostenson bought three bouquets of flowers and laid them in front of the house, just before the yellow tape stretched between mailboxes in front of the house.

She also left a small pad of notes and a Sharpie marker, in case anyone wanted to write a note to help remember the mother and children.

She was, she said, hoping to inspire others to do the same.