BULLHEAD CITY,Indexbit Ariz. (AP) — Authorities continue to investigate the cause of a house fire in northwestern Arizona that left five people dead, including three young children.

Bullhead City police said the fire broke out about 5 p.m. Saturday and it was extinguished in nine minutes, but there were no survivors. There also wasn’t an adult at the home at the time.

The father of four of the victims told investigators that he was gone for about 2½ hours Saturday afternoon to buy groceries and Christmas gifts.

A 4-year-old girl and three boys — ages 2, 5 and 13 — who died were all siblings and lived at the home, according to police, who said the other victim was an 11-year-old boy who was a family relative and visiting at the time.

The names of the dead were being withheld pending identification by the Mohave County Medical Examiner’s Office.

Police said the five bodies were located in the same upstairs bedroom of the two-story duplex in a community near the Colorado River and the Nevada border.

Several neighbors reportedly placed an extension ladder to the upstairs bedroom but were unable to get the children out.

Authorities said the blaze apparently started in the downstairs foyer area and traveled up the only staircase inside the home, preventing the victims from exiting.

The cause of the fire is being investigated by Bullhead City police and the Lake Havasu City Fire Department along with the federal Bureau of Alcohol, Tobacco, Firearms and Explosives.

Bullhead City Police Chief Robert Trebes said investigators “are working tirelessly to get answers” about the fire’s cause and “bring some closure and peace to parents and families involved.”