The five children who died in an Arizona house fire over the weekend were unsupervised after the father of four of them left to go holiday shopping, police said.

The children were not identified but were described as boys 2, 5, 11 and 13, and a girl who was 4, Bullhead City police said in a Monday update on the investigation into the fire’s cause. The 11-year-old was described as a relative visiting the household.

“The children’s father reported to investigators that he was gone for approximately 2.5 hours to buy groceries and Christmas gifts,” the police department said in its statement.

The blaze was reported at 4:54 p.m Saturday, and neighbors used a ladder in an attempt to rescue those inside before first responders arrived, police said.

Firefighters were at the scene within five minutes, police said, and at 5:03 p.m. declared the blaze was out. The police statement indicated the children had little chance of getting out alive.

“The initial fire investigation has revealed that the fire originated in the downstairs foyer area, most likely making it impossible for the children in the upstairs bedroom to get out of the residence safely,” the Bullhead City Police Department said.

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“The fire traveled up the only staircase inside the home, preventing the victims from exiting,” the police statement continued.

A final determination on the cause of the blaze remained under investigation.

In a video address, Bullhead City Police Chief Robert Trebes called the fire a “horrific tragedy” that has resonated throughout the community on the Colorado river near the Nevada and California borders.

“Like you, we want answers, too, to try to understand what happened and bring some closure and peace to parents and families involved,” Trebes said.

Because a city fire employee is the grandfather of the victims, outside investigators — the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives and the Lake Havasu City Fire Department — were called to join the probe alongside the Bullhead City Police Department, the police department said.

That relative was not identified.